Neprilysin inhibitors

ABSTRACT

In one aspect, the invention relates to compounds having the formula: 
     
       
         
         
             
             
         
       
     
     where R 1 -R 6 , a, b, and Z are as defined in the specification, or a pharmaceutically acceptable salt thereof. These compounds have neprilysin inhibition activity. In another aspect, the invention relates to pharmaceutical compositions comprising such compounds; methods of using such compounds; and processes and intermediates for preparing such compounds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/554,625, filed on Nov. 2, 2011; the entire disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to novel compounds having neprilysin-inhibition activity. The invention also relates to pharmaceutical compositions comprising such compounds, processes and intermediates for preparing such compounds and methods of using such compounds to treat diseases such as hypertension, heart failure, pulmonary hypertension, and renal disease.

2. State of the Art Neprilysin (neutral endopeptidase, EC 3.4.24.11) (NEP), is an endothelial membrane bound Zn²⁺ metallopeptidase found in many organs and tissues, including the brain, kidneys, lungs, gastrointestinal tract, heart, and the peripheral vasculature. NEP degrades and inactivates a number of endogenous peptides, such as enkephalins, circulating bradykinin, angiotensin peptides, and natriuretic peptides, the latter of which have several effects including, for example, vasodilation and natriuresis/diuresis, as well as inhibition of cardiac hypertrophy and ventricular fibrosis. Thus, NEP plays an important role in blood pressure homeostasis and cardiovascular health.

NEP inhibitors, such as thiorphan, candoxatril, and candoxatrilat, have been studied as potential therapeutics. Compounds that inhibit both NEP and angiotensin-I converting enzyme (ACE) are also known, and include omapatrilat, gempatrilat, and sampatrilat.

Referred to as vasopeptidase inhibitors, this latter class of compounds is described in Robl et al. (1999) Exp. Opin. Ther. Patents 9(12): 1665-1677.

Ksander et al. (1995) J. Med. Chem. 38:1689-1700 describes dicarboxylic acid dipeptide NEP inhibitors of the formula:

Compound R IC₅₀ (nM) 21g —C(O)—CH₂—COOH 92 21a (R, S) —C(O)—(CH₂)₂—COOH 5 21b (S, R) —C(O)—(CH₂)₂—COOH 190 21c (R, R) —C(O)—(CH₂)₂—COOH 700 21d (S, S) —C(O)—(CH₂)₂—COOH 27 21e —C(O)—(CH₂)₃—COOH 90 21f —C(O)—(CH₂)₄—COOH 324 Compound 21a, which has a succinic acid substituent, is the most active compound, with an IC₅₀ of 5 nM. The authors observed that “the succinic acid in the P₂′ site appears to be optimal since extension of the carboxylic acid chain by one (21e) and two (21f) methylene units decreased activity 18- and 65-fold.” The authors further noted that “decreasing the chain length by one methylene (21g) also showed an 18-fold decrease in activity.” (page 1692, 2^(nd) column).

SUMMARY OF THE INVENTION

The present invention provides novel compounds that have been found to possess neprilysin (NEP) enzyme inhibition activity. Accordingly, compounds of the invention are expected to be useful and advantageous as therapeutic agents for treating conditions such as hypertension and heart failure.

One aspect of the invention relates to a compound of formula I:

where:

R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹¹R¹², —CH(R¹⁵)—NH₂, —CH(R¹⁵)—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R¹¹ and R¹² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R¹¹ and R¹² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R¹³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹¹R¹²; and R¹⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; R¹⁵ is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl;

R² is —OR²¹ or —CH₂OR²¹; and R³ is H or —CH₃; where R²¹ is H, —C(O)—C₁₋₆alkyl, —C(O)—CH(R²²)—NH₂, —C(O)—CH(R²²)—NHC(O)O—C₁₋₆alkyl, or —P(O)(OR²³)₂; R²² is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl; R²³ is H, —C₁₋₆alkyl, or phenyl; or

R² is taken together with R¹ to form —OCR¹⁵R¹⁶— or —CH₂O—CR¹⁵R¹⁶—, and R³ is selected from H and —CH₃, where R¹⁵ and R¹⁶ are independently selected from H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or R¹⁵ and R¹⁶ are taken together to form ═O; or

R² is taken together with R³ to form —CH₂—O—CH₂— or —CH₂—CH₂—; or

R² and R³ are both —CH₃;

Z is selected from —CH— and —N—;

R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R⁴⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR⁴¹R⁴², —CH(R⁴⁵)—NH₂, —CH(R⁴⁵)—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R⁴¹ and R⁴² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R⁴¹ and R⁴² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R⁴³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR⁴¹R⁴²; and R⁴⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; R⁴⁵ is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl;

a is 0 or 1; R⁵ is selected from halo, —CH₃, —CF₃, and —CN;

b is 0 or an integer from 1 to 3; each R⁶ is independently selected from halo, —OH, —CH₃, —OCH₃, —CN, and —CF₃;

where each alkyl group in R¹ and R⁴ is optionally substituted with 1 to 8 fluoro atoms; and where the methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl;

or a pharmaceutically acceptable salt thereof.

Another aspect of the invention relates to pharmaceutical compositions comprising a pharmaceutically acceptable carrier and a compound of the invention. Such compositions may optionally contain other therapeutic agents. Accordingly, in yet another aspect of the invention, a pharmaceutical composition comprises a compound of the invention as the first therapeutic agent, one or more secondary therapeutic agent, and a pharmaceutically acceptable carrier. Another aspect of the invention relates to a combination of active agents, comprising a compound of the invention and a second therapeutic agent. The compound of the invention can be formulated together or separately from the additional agent(s). When formulated separately, a pharmaceutically acceptable carrier may be included with the additional agent(s). Thus, yet another aspect of the invention relates to a combination of pharmaceutical compositions, the combination comprising: a first pharmaceutical composition comprising a compound of the invention and a first pharmaceutically acceptable carrier; and a second pharmaceutical composition comprising a second therapeutic agent and a second pharmaceutically acceptable carrier. In another aspect, the invention relates to a kit containing such pharmaceutical compositions, for example where the first and second pharmaceutical compositions are separate pharmaceutical compositions.

Compounds of the invention possess NEP enzyme inhibition activity, and are therefore expected to be useful as therapeutic agents for treating patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme or by increasing the levels of its peptide substrates. Thus, one aspect of the invention relates to a method of treating patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme, comprising administering to a patient a therapeutically effective amount of a compound of the invention. Another aspect of the invention relates to a method of treating hypertension, heart failure, or renal disease, comprising administering to a patient a therapeutically effective amount of a compound of the invention. Still another aspect of the invention relates to a method for inhibiting a NEP enzyme in a mammal comprising administering to the mammal, a NEP enzyme-inhibiting amount of a compound of the invention.

Since compounds of the invention possess NEP inhibition activity, they are also useful as research tools. Accordingly, one aspect of the invention relates to a method of using a compound of the invention as a research tool, the method comprising conducting a biological assay using a compound of the invention. Compounds of the invention can also be used to evaluate new chemical compounds. Thus another aspect of the invention relates to a method of evaluating a test compound in a biological assay, comprising: (a) conducting a biological assay with a test compound to provide a first assay value; (b) conducting the biological assay with a compound of the invention to provide a second assay value; wherein step (a) is conducted either before, after or concurrently with step (b); and (c) comparing the first assay value from step (a) with the second assay value from step (b). Exemplary biological assays include a NEP enzyme inhibition assay. Still another aspect of the invention relates to a method of studying a biological system or sample comprising a NEP enzyme, the method comprising: (a) contacting the biological system or sample with a compound of the invention; and (b) determining the effects caused by the compound on the biological system or sample.

Yet another aspect of the invention relates to processes and intermediates useful for preparing compounds of the invention. Accordingly, another aspect of the invention relates to a process of preparing compounds of formula I, comprising the step of coupling a compound of formula 1 with a compound of formula 2:

to produce a compound of formula I; where P is H or an amino-protecting group selected from t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; and where the process further comprises deprotecting the compound of formula 1 when P is an amino protecting group; and where R¹-R⁶, a, b, and Z are as defined for formula I. Another aspect of the invention relates to a process of preparing a pharmaceutically acceptable salt of a compound of formula I, comprising contacting a compound of formula I in free acid or base form with a pharmaceutically acceptable base or acid. In other aspects, the invention relates to products prepared by any of the processes described herein, as well as novel intermediates used in such process. In one aspect of the invention novel intermediates have formula 1 or a salt thereof, as defined herein.

Yet another aspect of the invention relates to the use of a compound of formula I or a pharmaceutically acceptable salt thereof, for the manufacture of a medicament, especially for the manufacture of a medicament useful for treating hypertension, heart failure, or renal disease. Another aspect of the invention relates to use of a compound of the invention for inhibiting a NEP enzyme in a mammal. Still another aspect of the invention relates to the use of a compound of the invention as a research tool. Other aspects and embodiments of the invention are disclosed herein.

A particular group of compounds of formula I are those disclosed in U.S. Provisional Application No. 61/554,625, filed on Nov. 2, 2011. This group includes compounds of formula I′; wherein:

where: R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹¹R¹², —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R¹¹ and R¹² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R¹¹ and R¹² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R¹³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹¹R¹²; and R¹⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; R² is selected from —OH, —CH₂OH, —OP(O)(OH)₂, and —CH₂OP(O)(OH)₂; and R³ is selected from H and —CH₃; or R² is taken together with R¹ to form —OCR¹⁵R¹⁶— or —CH₂O—CR¹⁵R¹⁶—, and R³ is selected from H and —CH₃, where R¹⁵ and R¹⁶ are independently selected from H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or R¹⁵ and R¹⁶ are taken together to form ═O; or R² is taken together with R³ to form —CH₂—O—CH₂— or —CH₂—CH₂—; or R² and R³ are both —CH₃; Z is selected from —CH— and —N—; R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R⁴⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR⁴¹R⁴², —CH[CH(CH₃)₂]—NH₂, —CH[CH(CH₃)₂]—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R⁴¹ and R⁴² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R⁴¹ and R⁴² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—R⁴³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR⁴¹R⁴²; and R⁴⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; a is 0 or 1; R⁵ is selected from halo, —CH₃, —CF₃, and —CN; b is 0 or an integer from 1 to 3; each R⁶ is independently selected from halo, —OH, —CH₃, —OCH₃, and —CF₃; and where each alkyl group in R¹ and R⁴ is optionally substituted with 1 to 8 fluoro atoms; and; where the methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl; or a pharmaceutically acceptable salt thereof.

DETAILED DESCRIPTION OF THE INVENTION Definitions

When describing the compounds, compositions, methods and processes of the invention, the following terms have the following meanings unless otherwise indicated. Additionally, as used herein, the singular forms “a,” “an,” and “the” include the corresponding plural forms unless the context of use clearly dictates otherwise. The terms “comprising”, “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. All numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used herein are to be understood as being modified in all instances by the term “about,” unless otherwise indicated. Accordingly, the numbers set forth herein are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each number should at least be construed in light of the reported significant digits and by applying ordinary rounding techniques.

The term “alkyl” means a monovalent saturated hydrocarbon group which may be linear or branched. Unless otherwise defined, such alkyl groups typically contain from 1 to 10 carbon atoms and include, for example, —C₁₋₄alkyl, —C₁₋₅alkyl, —C₂₋₅alkyl, —C₁₋₆alkyl, —C₁₋₈alkyl, and —C₁₋₁₀alkyl. Representative alkyl groups include, by way of example, methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl and the like.

When a specific number of carbon atoms is intended for a particular term used herein, the number of carbon atoms is shown preceding the term as subscript. For example, the term “—C₁₋₆alkyl” means an alkyl group having from 1 to 6 carbon atoms, and the term “—C₃₋₇cycloalkyl” means a cycloalkyl group having from 3 to 7 carbon atoms, respectively, where the carbon atoms are in any acceptable configuration.

The term “alkylene” means a divalent saturated hydrocarbon group that may be linear or branched. Unless otherwise defined, such alkylene groups typically contain from 0 to 10 carbon atoms and include, for example, —C₀₋₁alkylene-, —C₀₋₆alkylene-, —C₁₋₃alkylene-, and —C₁₋₆alkylene-. Representative alkylene groups include, by way of example, methylene, ethane-1,2-diyl (“ethylene”), propane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,5-diyl and the like. It is understood that when the alkylene term include zero carbons such as —C₀₋₁alkylene-, such terms are intended to include the absence of carbon atoms, that is, the alkylene group is not present except for a covalent bond attaching the groups separated by the alkylene term.

The term “aryl” means a monovalent aromatic hydrocarbon having a single ring (i.e., phenyl) or one or more fused rings. Fused ring systems include those that are fully unsaturated (e.g., naphthalene) as well as those that are partially unsaturated (e.g., 1,2,3,4-tetrahydronaphthalene). Unless otherwise defined, such aryl groups typically contain from 6 to 10 carbon ring atoms and include, for example, —C₆₋₁₀aryl. Representative aryl groups include, by way of example, phenyl and naphthalene-1-yl, naphthalene-2-yl, and the like.

The term “cycloalkyl” means a monovalent saturated carbocyclic hydrocarbon group. Unless otherwise defined, such cycloalkyl groups typically contain from 3 to 10 carbon atoms and include, for example, —C₃₋₅cycloalkyl, —C₃₋₆cycloalkyl and —C₃₋₇cycloalkyl. Representative cycloalkyl groups include, by way of example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.

The term “halo” means fluoro, chloro, bromo and iodo.

The term “heteroaryl” is intended to mean a monovalent unsaturated (aromatic) heterocycle having a single ring or two fused rings. Monovalent unsaturated heterocycles are also commonly referred to as “heteroaryl” groups. Unless otherwise defined, heteroaryl groups typically contain from 5 to 10 total ring atoms, of which 1 to 9 are ring carbon atoms, and 1 to 4 are ring heteroatoms, and include, for example, —C₁₋₉heteroaryl and —C₅₋₉heteroaryl. Representative heteroaryl groups include, by way of example, pyrrole (e.g., 3-pyrrolyl and 2H-pyrrol-3-yl), imidazole (e.g., 2-imidazolyl), furan (e.g., 2-furyl and 3-furyl), thiophene (e.g., 2-thienyl), triazole (e.g., 1,2,3-triazolyl and 1,2,4-triazolyl), pyrazole (e.g., 1H-pyrazol-3-yl), oxazole (e.g., 2-oxazolyl), isoxazole (e.g., 3-isoxazolyl), thiazole (e.g., 2-thiazolyl and 4-thiazolyl), and isothiazole (e.g., 3-isothiazolyl), pyridine (e.g., 2-pyridyl, 3-pyridyl, and 4-pyridyl), pyridylimidazole, pyridyltriazole, pyrazine, pyridazine (e.g., 3-pyridazinyl), pyrimidine (e.g., 2-pyrimidinyl), tetrazole, triazine (e.g., 1,3,5-triazinyl), indolyle (e.g., 1H-indol-2-yl, 1H-indol-4-yl and 1H-indol-5-yl), benzofuran (e.g., benzofuran-5-yl), benzothiophene (e.g., benzo[b]thien-2-yl and benzo[b]thien-5-yl), benzimidazole, benzoxazole, benzothiazole, benzotriazole, quinoline (e.g., 2-quinolyl), isoquinoline, quinazoline, quinoxaline and the like.

The term “optionally substituted” means that group in question may be unsubstituted or it may be substituted one or several times, such as 1 to 3 times, or 1 to 5 times, or 1 to 8 times. For example, an alkyl group that is “optionally substituted” with fluoro atoms may be unsubstituted, or it may contain 1, 2, 3, 4, 5, 6, 7, or 8 fluoro atoms. Similarly, a group that is “optionally substituted” with one or two —C₁₋₆alkyl groups, may be unsubstituted, or it may contain one or two —C₁₋₆alkyl groups.

As used herein, the phrase “having the formula” or “having the structure” is not intended to be limiting and is used in the same way that the term “comprising” is commonly used. For example, if one structure is depicted, it is understood that all stereoisomer and tautomer forms are encompassed, unless stated otherwise.

The term “pharmaceutically acceptable” refers to a material that is not biologically or otherwise unacceptable when used in the invention. For example, the term “pharmaceutically acceptable carrier” refers to a material that can be incorporated into a composition and administered to a patient without causing unacceptable biological effects or interacting in an unacceptable manner with other components of the composition. Such pharmaceutically acceptable materials typically have met the required standards of toxicological and manufacturing testing, and include those materials identified as suitable inactive ingredients by the U.S. Food and Drug administration.

The term “pharmaceutically acceptable salt” means a salt prepared from a base or an acid which is acceptable for administration to a patient, such as a mammal (for example, salts having acceptable mammalian safety for a given dosage regime). However, it is understood that the salts covered by the invention are not required to be pharmaceutically acceptable salts, such as salts of intermediate compounds that are not intended for administration to a patient. Pharmaceutically acceptable salts can be derived from pharmaceutically acceptable inorganic or organic bases and from pharmaceutically acceptable inorganic or organic acids. In addition, when a compound of formula I contains both a basic moiety, such as an amine, pyridine or imidazole, and an acidic moiety such as a carboxylic acid or tetrazole, zwitterions may be formed and are included within the term “salt” as used herein. Salts derived from pharmaceutically acceptable inorganic bases include ammonium, calcium, copper, ferric, ferrous, lithium, magnesium, manganic, manganous, potassium, sodium, and zinc salts, and the like. Salts derived from pharmaceutically acceptable organic bases include salts of primary, secondary and tertiary amines, including substituted amines, cyclic amines, naturally-occurring amines and the like, such as arginine, betaine, caffeine, choline, N,N-dibenzylethylenediamine, diethylamine, 2-diethylaminoethanol, 2-dimethylaminoethanol, ethanolamine, ethylenediamine, N-ethylmorpholine, N-ethylpiperidine, glucamine, glucosamine, histidine, hydrabamine, isopropylamine, lysine, methylglucamine, morpholine, piperazine, piperadine, polyamine resins, procaine, purines, theobromine, triethylamine, trimethylamine, tripropylamine, tromethamine and the like. Salts derived from pharmaceutically acceptable inorganic acids include salts of boric, carbonic, hydrohalic (hydrobromic, hydrochloric, hydrofluoric or hydroiodic), nitric, phosphoric, sulfamic and sulfuric acids. Salts derived from pharmaceutically acceptable organic acids include salts of aliphatic hydroxyl acids (for example, citric, gluconic, glycolic, lactic, lactobionic, malic, and tartaric acids), aliphatic monocarboxylic acids (for example, acetic, butyric, formic, propionic and trifluoroacetic acids), amino acids (for example, aspartic and glutamic acids), aromatic carboxylic acids (for example, benzoic, p-chlorobenzoic, diphenylacetic, gentisic, hippuric, and triphenylacetic acids), aromatic hydroxyl acids (for example, o-hydroxybenzoic, p-hydroxybenzoic, 1-hydroxynaphthalene-2-carboxylic and 3-hydroxynaphthalene-2-carboxylic acids), ascorbic, dicarboxylic acids (for example, fumaric, maleic, oxalic and succinic acids), glucoronic, mandelic, mucic, nicotinic, orotic, pamoic, pantothenic, sulfonic acids (for example, benzenesulfonic, camphosulfonic, edisylic, ethanesulfonic, isethionic, methanesulfonic, naphthalenesulfonic, naphthalene-1,5-disulfonic, naphthalene-2,6-disulfonic and p-toluenesulfonic acids), xinafoic acid, and the like.

As used herein, the term “prodrug” is generally intended to mean an inactive precursor of a drug that is converted into its active form in the body under physiological conditions, for example, by normal metabolic processes. Such compounds may not possess pharmacological activity at NEP, but may be administered orally or parenterally and thereafter metabolized in the body to form compounds that are pharmacologically active at NEP. When orally administered, such compounds may also provide a better fraction absorbed (i.e., better pK properties) for renal delivery, as compared to oral administration of the active form. Exemplary prodrugs include esters such as C₁₋₆alkylesters and aryl-C₁₋₆alkylesters. In one embodiment, the active compound has a free carboxyl and the prodrug is an ester derivative thereof, i.e., the prodrug is an ester such as —C(O)OCH₂CH₃. Such ester prodrugs are then converted by solvolysis or under physiological conditions to be the free carboxyl compound. The term “prodrug” is also intended to include a less active precursor of a drug that is converted into a more active form in the body. For example, certain prodrugs may possess pharmacological activity at NEP, but not necessarily at the desired level; such compounds are converted in the body into a form having the desired level of activity. The term is also intended to include certain protected derivatives of compounds of formula I that may be made prior to a final deprotection stage. Thus, all protected derivatives and prodrugs of compounds formula I are included within the scope of the invention.

The term “therapeutically effective amount” means an amount sufficient to effect treatment when administered to a patient in need thereof, that is, the amount of drug needed to obtain the desired therapeutic effect. For example, a therapeutically effective amount for treating hypertension is an amount of compound needed to, for example, reduce, suppress, eliminate, or prevent the symptoms of hypertension, or to treat the underlying cause of hypertension. In one embodiment, a therapeutically effective amount is that amount of drug needed to reduce blood pressure or the amount of drug needed to maintain normal blood pressure. On the other hand, the term “effective amount” means an amount sufficient to obtain a desired result, which may not necessarily be a therapeutic result. For example, when studying a system comprising a NEP enzyme, an “effective amount” may be the amount needed to inhibit the enzyme.

The term “treating” or “treatment” as used herein means the treating or treatment of a disease or medical condition (such as hypertension) in a patient, such as a mammal (particularly a human) that includes one or more of the following: (a) preventing the disease or medical condition from occurring, i.e., preventing the reoccurrence of the disease or medical condition or prophylactic treatment of a patient that is pre-disposed to the disease or medical condition; (b) ameliorating the disease or medical condition, i.e., eliminating or causing regression of the disease or medical condition in a patient; (c) suppressing the disease or medical condition, i.e., slowing or arresting the development of the disease or medical condition in a patient; or (d) alleviating the symptoms of the disease or medical condition in a patient. For example, the term “treating hypertension” would include preventing hypertension from occurring, ameliorating hypertension, suppressing hypertension, and alleviating the symptoms of hypertension (for example, lowering blood pressure). The term “patient” is intended to include those mammals, such as humans, that are in need of treatment or disease prevention or that are presently being treated for disease prevention or treatment of a specific disease or medical condition, as well as test subjects in which compounds of the invention are being evaluated or being used in an assay, for example an animal model.

All other terms used herein are intended to have their ordinary meaning as understood by those of ordinary skill in the art to which they pertain.

In one aspect, the invention relates to compounds of formula I:

or a pharmaceutically acceptable salt thereof.

As used herein, the term “compound of the invention” includes all compounds encompassed by formula I such as the species embodied in formulas Ia and Ib, as well as the compounds encompassed by formulas IIa-IIk, IIIa-IIIb, and IVa-IVd. In addition, the compounds of the invention may also contain several basic or acidic groups (for example, amino or carboxyl groups) and therefore, such compounds can exist as a free base, free acid, or in various salt forms. All such salt forms are included within the scope of the invention. Furthermore, the compounds of the invention may also exist as prodrugs. Accordingly, those skilled in the art will recognize that reference to a compound herein, for example, reference to a “compound of the invention” or a “compound of formula I” includes a compound of formula I as well as pharmaceutically acceptable salts and prodrugs of that compound unless otherwise indicated. Further, the term “or a pharmaceutically acceptable salt and/or prodrug thereof” is intended to include all permutations of salts and prodrugs, such as a pharmaceutically acceptable salt of a prodrug. Furthermore, solvates of compounds of formula I are included within the scope of this invention.

The compounds of formula I may contain one or more chiral centers and therefore, these compounds may be prepared and used in various stereoisomeric forms. Accordingly, the invention also relates to racemic mixtures, pure stereoisomers (e.g., enantiomers and diastereoisomers), stereoisomer-enriched mixtures, and the like unless otherwise indicated. When a chemical structure is depicted herein without any stereochemistry, it is understood that all possible stereoisomers are encompassed by such structure. Thus, for example, the terms “compound of formula I,” “compounds of formula II,” and so forth, are intended to include all possible stereoisomers of the compound. Similarly, when a particular stereoisomer is shown or named herein, it will be understood by those skilled in the art that minor amounts of other stereoisomers may be present in the compositions of the invention unless otherwise indicated, provided that the utility of the composition as a whole is not eliminated by the presence of such other isomers. Individual stereoisomers may be obtained by numerous methods that are well known in the art, including chiral chromatography using a suitable chiral stationary phase or support, or by chemically converting them into diastereoisomers, separating the diastereoisomers by conventional means such as chromatography or recrystallization, then regenerating the original stereoisomer.

Additionally, where applicable, all cis-trans or E/Z isomers (geometric isomers), tautomeric forms and topoisomeric forms of the compounds of the invention are included within the scope of the invention unless otherwise specified.

More specifically, compounds of formula I can contain at least two chiral centers when the “Z” moiety is —CH—, and can contain at least one chiral center when the “Z” moiety is —N—. These chiral centers are indicated by the symbols * and ** in the following formulas Ia and Ib:

Note however, that there is no * chiral center when R² is taken together with R³ to form —CH₂—O—CH₂— or —CH₂—CH₂—, or R² and R³ are both —CH₃.

In one stereoisomer of the compound of formula Ia, both carbon atoms identified by the * and ** symbols have the (R) configuration. In this embodiment, compounds have the (R,R) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (R,R) configuration at these carbon atoms. In another stereoisomer of the compound of formula Ia, both carbon atoms identified by the * and ** symbols have the (S) configuration. In this embodiment, compounds have the (S,S) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (S,S) configuration at these carbon atoms. In yet another stereoisomer of the compound of formula Ia, the carbon atom identified by the symbol * has the (S) configuration and the carbon atom identified by the symbol ** has the (R) configuration. In this embodiment, compounds have the (S,R) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (S,R) configuration at these carbon atoms. In still another stereoisomer of the compound of formula Ia, the carbon atom identified by the symbol * has the (R) configuration and the carbon atom identified by the symbol ** has the (S) configuration. In this embodiment, compounds have the (R,S) configuration at the * and ** carbon atoms or are enriched in a stereoisomeric form having the (R,S) configuration at these carbon atoms.

In one stereoisomer of the compound of formula Ib, the carbon atom identified by the * symbol has the (R) configuration. In this embodiment, compounds have the (R) configuration at the * carbon atom or are enriched in a stereoisomeric form having the (R) configuration at this carbon atom. In another stereoisomer of the compound of formula Ib, the carbon atom identified by the * symbol has the (S) configuration. In this embodiment, compounds have the (S) configuration at the * carbon atom or are enriched in a stereoisomeric form having the (S) configuration at this carbon atom.

These various embodiments can be shown as formula Ia-1:

Formula R² R³ * ** Ia-1 —OR²¹ H (R) (R) Ia-1 —OR²¹ —CH₃ (R) (R) Ia-1 —CH₂OR²¹ H (S) (S) Ia-1 —CH₂OR²¹ —CH₃ (S) (R) Ia-1 R² is taken together with R¹ to form H (R) (R) —OCR¹⁵R¹⁶— Ia-1 R² is taken together with R¹ to form —CH₃ (R) (R) —OCR¹⁵R¹⁶— Ia-1 R² is taken together with R¹ to form H (S) (S) —CH₂O—CR¹⁵R¹⁶— Ia-1 R² is taken together with R¹ to form —CH₃ (R) (S) —CH₂O—CR¹⁵R¹⁶— Ia-2 —OR²¹ H (S) (S) Ia-2 —OR²¹ —CH₃ (S) (S) Ia-2 —CH₂OR²¹ H (R) (R) Ia-2 —CH₂OR²¹ —CH₃ (R) (S) Ia-2 R² is taken together with R¹ to form H (S) (S) —OCR¹⁵R¹⁶— Ia-2 R² is taken together with R¹ to form —CH₃ (S) (S) —OCR¹⁵R¹⁶— Ia-2 R² is taken together with R¹ to form H (R) (R) —CH₂O—CR¹⁵R¹⁶— Ia-2 R² is taken together with R¹ to form —CH₃ (S) (R) -CH₂O—CR¹⁵R¹⁶— Ia-3 —OR²¹ H (S) (R) Ia-3 —OR²¹ —CH₃ (S) (R) Ia-3 —CH₂OR²¹ H (R) (S) Ia-3 —CH₂OR²¹ —CH₃ (R) (R) Ia-3 R² is taken together with R¹ to form H (R) (S) —OCR¹⁵R¹⁶— Ia-3 R² is taken together with R¹ to form —CH₃ (R) (S) —OCR¹⁵R¹⁶— Ia-3 R² is taken together with R¹ to form H (S) (R) —CH₂O—CR¹⁵R¹⁶— Ia-3 R² is taken together with R¹ to form —CH₃ (R) (R) —CH₂O—CR¹⁵R¹⁶— Ia-4 —OR²¹ H (R) (S) Ia-4 —OR²¹ —CH₃ (R) (S) Ia-4 —CH₂OR²¹ H (S) (R) Ia-4 —CH₂OR²¹ —CH₃ (S) (S) Ia-4 R² is taken together with R¹ to form H (S) (R) —OCR¹⁵R¹⁶— Ia-4 R² is taken together with R¹ to form —CH₃ (S) (R) —OCR¹⁵R¹⁶— Ia-4 R² is taken together with R¹ to form H (R) (S) —CH₂O—CR¹⁵R¹⁶— Ia-4 R² is taken together with R¹ to form —CH₃ (S) (S) —CH₂O—CR¹⁵R¹⁶— Ib-1 —OR²¹ H (R) NA Ib-1 —OR²¹ —CH₃ (R) NA Ib-1 —CH₂OR²¹ H (S) NA Ib-1 —CH₂OR²¹ —CH₃ (S) NA Ib-1 R² is taken together with R¹ to form H (R) NA —OCR¹⁵R¹⁶— Ib-1 R² is taken together with R¹ to form —CH₃ (R) NA —OCR¹⁵R¹⁶— Ib-1 R² is taken together with R¹ to form H (S) NA —CH₂O—CR¹⁵R¹⁶— Ib-1 R² is taken together with R¹ to form —CH₃ (S) NA —CH₂O—CR¹⁵R¹⁶— Ib-2 —OR²¹ H (S) NA Ib-2 —OR²¹ —CH₃ (S) NA Ib-2 —CH₂OR²¹ H (R) NA Ib-2 —CH₂OR²¹ —CH₃ (R) NA Ib-2 R² is taken together with R¹ to form H (S) NA —OCR¹⁵R¹⁶— Ib-2 R² is taken together with R¹ to form —CH₃ (S) NA —OCR¹⁵R¹⁶— Ib-2 R² is taken together with R¹ to form H (R) NA —CH₂O—CR¹⁵R¹⁶— Ib-2 R² is taken together with R¹ to form —CH₃ (R) NA —CH₂O—CR¹⁵R¹⁶—

In some embodiments, in order to optimize the therapeutic activity of the compounds of the invention, e.g., to treat hypertension, it may be desirable that the carbon atoms identified by the * and ** symbols have a particular configuration or are enriched in a stereoisomeric form having such configuration. Thus, in certain aspects, this invention relates to each individual enantiomer or to an enantiomer-enriched mixture of enantiomers comprising predominately one enantiomer or the other enantiomer. In other embodiments, the compounds of the invention are present as racemic mixtures of enantiomers.

The compounds of the invention, as well as those compounds used in their synthesis, may also include isotopically-labeled compounds, that is, where one or more atoms have been enriched with atoms having an atomic mass different from the atomic mass predominately found in nature. Examples of isotopes that may be incorporated into the compounds of formula I, for example, include, but are not limited to, ²H, ³H, ¹³C, ¹⁴C, ¹⁵N, ¹⁸O, ¹⁷O, ³⁵S, ³⁶Cl, and ¹⁸F. Of particular interest are compounds of formula I enriched in tritium or carbon-14 which can be used, for example, in tissue distribution studies; compounds of formula I enriched in deuterium especially at a site of metabolism resulting, for example, in compounds having greater metabolic stability; and compounds of formula I enriched in a positron emitting isotope, such as ¹¹C, ¹⁸F, ¹⁵O and ¹³N, which can be used, for example, in Positron Emission Topography (PET) studies.

The nomenclature used herein to name the compounds of the invention is illustrated in the Examples herein. This nomenclature has been derived using the commercially available AutoNom software (MDL, San Leandro, Calif.).

Representative Embodiments

The following substituents and values are intended to provide representative examples of various aspects and embodiments of the invention. These representative values are intended to further define and illustrate such aspects and embodiments and are not intended to exclude other embodiments or to limit the scope of the invention. In this regard, the representation that a particular value or substituent is preferred is not intended in any way to exclude other values or substituents from the invention unless specifically indicated.

In one aspect, this invention relates to compounds of formula I:

The R¹ moiety is selected from:

H;

—C₁₋₈alkyl, e.g., —CH₃, —CH₂CH₃, —(CH₂)₂CH₃, —CH(CH₃)₂, —C(CH₃)₃, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₄CH₃, —(CH₂)₂CH(CH₃)₂, —(CH₂)₅CH₃, and —(CH₂)₆CH₃;

—C₁₋₃alkylene-C₆₋₁₀aryl, e.g., benzyl;

—C₁₋₃alkylene-C₁₋₉heteroaryl, e.g., —CH₂-pyridinyl and —(CH₂)₂-pyridinyl;

—C₃₋₇cycloalkyl, e.g., cyclopentyl;

—[(CH₂)₂O]₁₋₃CH₃, e.g., —(CH₂)₂OCH₃ and —[(CH₂)₂O]₂CH₃;

—C₁₋₆alkylene-OC(O)R¹⁰, e.g., —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂CH(CH₃)OC(O)CH₂CH₃, —CH₂OC(O)OCH₃, —CH₂OC(O)OCH₂CH₃, —CH(CH₃)OC(O)OCH₂CH₃, —CH(CH₃)OC(O)O—CH(CH₃)₂, —CH₂CH(CH₃)OC(O)-cyclopentyl, —CH₂OC(O)O-cyclopropyl, —CH(CH₃)—OC(O)—O-cyclohexyl, —CH₂OC(O)O-cyclopentyl, —CH₂CH(CH₃)OC(O)-phenyl, —CH₂OC(O)O-phenyl, —CH₂OC(O)—CH[CH(CH₃)₂]—NH₂, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)OCH₃, and —CH(CH₃)OC(O)—CH(NH₂)CH₂COOCH₃;

—C₁₋₆alkylene-NR¹¹R¹², e.g., —(CH₂)₂—N(CH₃)₂, and

—C₁₋₆alkylene-C(O)R¹³, e.g., —CH₂C(O)OCH₃, —CH₂C(O)O-benzyl, —CH₂C(O)—N(CH₃)₂, and

—C₀₋₆alkylenemorpholine, e.g., —(CH₂)₂-morpholine and —(CH₂)₃-morpholine:

—C₁₋₆alkylene-SO₂—C₁₋₆alkyl, e.g., —(CH₂)₂SO₂CH₃;

The R¹⁰ moiety is selected from:

-   -   —C₁₋₆alkyl, e.g., —CH₃ and —CH₂CH₃;     -   —O—C₁₋₆alkyl, e.g., —OCH₃, —O—CH₂CH₃, and —O—CH(CH₃)₂;     -   —C₃₋₇cycloalkyl, e.g., cyclopentyl);     -   —O—C₃₋₇cycloalkyl, e.g., —O-cyclopropyl, —O-cyclohexyl, and         —O-cyclopentyl; phenyl;     -   —O-phenyl;     -   —NR¹¹R¹²;     -   —CH(R¹⁵)—NH₂, e.g., —CH[CH(CH₃)₂]—NH₂;     -   —CH(R¹⁵)—NHC(O)O—C₁₋₆alkyl, e.g., —CH[CH(CH₃)₂]—NHC(O)OCH₃; and     -   —CH(NH₂)CH₂COOCH₃.         The R¹¹ and R¹² moieties are independently selected from H,         —C₁₋₆alkyl (e.g., CH₃), and benzyl. Alternately, the R¹¹ and R¹²         moieties can be taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or         —(CH₂)₂O(CH₂)₂—, for example to form a group such as:

The R¹³ moiety is selected from —O—C₁₋₆alkyl, e.g., —OCH₃, —O-benzyl, and —NR¹¹R¹², e.g., —N(CH₃)₂, and

The R¹⁴ moiety is —C₁₋₆alkyl (e.g., —CH₃ and —C(CH₃)₃) or —C₀₋₆alkylene-C₆₋₁₀aryl. The R¹⁵ moiety is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl.

In addition, each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms. For example, when R¹ is —C₁₋₈alkyl, R¹ can also be a group such as —CH₂CF₃, —CH(CH₃)CF₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —CH₂CF₂CF₃, —CH(CF₃)₂, —CH(CH₂F)₂, —C(CF₃)₂CH₃, and —CH(CH₃)CF₂CF₃.

In one embodiment, R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₆alkylene-OC(O)R¹⁰, and

where R¹⁰ is —C₁₋₆alkyl, —O—C₁₋₆alkyl, or —CH[R¹⁵]—NHC(O)O—C₁₋₆alkyl; R¹⁴ is —C₁₋₆alkyl; R¹⁵ is —CH(CH₃)₂; and each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms. In one specific embodiment, R¹ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₆CH₃, —CH₂CF₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —CH₂CF₂CF₃, —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂OC(O)OCH₂CH₃, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)O—CH₃, and

where R¹⁴ is —CH₃. In other embodiments these compounds have formulas IIa-IId, IIi-IIk, IIIa-IIIb, and IVa-IVd.

In one embodiment, R¹ is H. In other embodiments these compounds have formulas IIa-IId, IIi-IIk, IIIa-IIIb, and IVa-IVd.

In another embodiment, R¹ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-Cl₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In other embodiments these compounds have formulas IIa-IId, IIi-IIk, IIIa-IIIb, and IVa-IVd. In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. Specific examples of such prodrug moieties include where R¹ is —C₁₋₆alkylene-OC(O)R¹⁰, such as —CH(CH₃)OC(O)—O-cyclohexyl:

making the compound a cilexetil ester; or R¹ is —C₀₋₆alkylenemorpholine such as —(CH₂)₂— morpholine:

making the compound a 2-morpholinoethyl or mofetil ester; or

such as —CH₂-5-methyl-[1,3]dioxol-2-one;

making the compound a medoxomil ester.

In one embodiment, R² is —OR²¹ or —CH₂OR²¹, and R³ is H or —CH₃. These embodiments can be depicted as formulas IIa-IId:

The R²¹ moiety is H, —C(O)—C₁₋₆alkyl, —C(O)—CH(R²²)—NH₂, —C(O)—CH(R²²)—NHC(O)O—C₁₋₆alkyl, or —P(O)(OR²³)₂; and in one particular embodiment, R²¹ moiety is H. The R²² moiety is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl. The R²³ moiety is H, —C₁₋₆alkyl, or phenyl.

In one embodiment, compounds of the invention have formula IIa, and in one exemplary embodiment, R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₆alkylene-OC(O)R¹⁰, and

where R¹⁰ is —C₁₋₆alkyl, —O—C₁₋₆alkyl, or —CH[R¹⁵]—NHC(O)O—C₁₋₆alkyl; R¹⁴ is —C₁₋₆alkyl; R¹⁵ is —CH(CH₃)₂; and each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms; Z is selected from —CH— and —N—; R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, and

where R⁴⁴ is —C₁₋₆alkyl; and each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms; a is 0 and b is 0; or a is 0, b is 1, and R⁶ is halo; or a is 0, b is 2, and one R⁶ is halo and the other R⁶ is halo or —CH₃; or a is 1, R⁵ is halo, and b is 0; or a is 1, R⁵ is halo, b is 1, and R⁶ is halo; or a is 1, R⁵ is halo, b is 2, and each R⁶ is halo; and where the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups; and in another exemplary embodiment, R¹ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₆CH₃, —CH₂CF₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —CH₂CF₂CF₃, —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂OC(O)OCH₂CH₃, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)O—CH₃, and

where R¹⁴ is —CH₃; R⁴ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —C(CH₃)₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —(CH₂)₃—O—CH₂CH₃, —(CH₂)₂—O-phenyl, —(CH₂)₂OCH₃, and

where R⁴⁴ is —CH₃; and a is 0 and b is 0; or a is 0, b is 1, and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro; or a is 0, b is 2, and R⁶ is 2′-fluoro, 5′-chloro or 2′-methyl, 5′-chloro or 2′,5′-dichloro; or a is 1, R⁵ is 3-chloro, and b is 0; or a is 1, R⁵ is 3-chloro, b is 1, and R⁶ is 3′-chloro; or a is 1, R⁵ is 3-chloro, b is 2, and R⁶ is 2′-fluoro, 5′-chloro.

In one embodiment, compounds of the invention have formula IIb, and in one exemplary embodiment, H or —C₁₋₈alkyl; Z is —N—; R⁴ is H or —C₁₋₈alkyl; and a and b are 0; and in another exemplary embodiment, R¹ and R⁴ are H.

In one embodiment, compounds of the invention have formula IIc, and in one exemplary embodiment, R¹ is H or —C₁₋₈alkyl; Z is —CH—; R⁴ is H or —C₁₋₈alkyl; a is 0 or a is 1 and R⁵ is halo; b is 0 or b is 1 or 2 and R⁶ is halo; and where the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups; and in another exemplary embodiment, R¹ is H, —CH₂CH₃, or —(CH₂)₃CH₃; R⁴ is H; a is 0 or a is 1 and R⁵ is 3-chloro; b is 0 or b is 1 and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro.

In one embodiment, compounds of the invention have formula IId, and in one exemplary embodiment, R¹ is H or —C₁₋₈alkyl; Z is —CH—; R⁴ is H or —C₁₋₈alkyl; a is 0; and b is 0, or b is 1 and R⁶ is halo; and in another exemplary embodiment, R¹ is H or —CH₂CH₃; R⁴ is H or —CH₂CH(CH₃)₂; and b is 0, or b is 1 and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro.

In another embodiment, R² is taken together with R¹ to form —OCR¹⁵R¹⁶— or —CH₂O—CR¹⁵R¹⁶—, and R³ is selected from H and —CH₃. The R¹⁵ and R¹⁶ moieties are independently selected from H, —C₁₋₆alkyl, and —O—C₃₋₇cycloalkyl, or R¹⁵ and R¹⁶ are taken together to form ═O. These can be depicted as formulas IIe-IIh:

In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. Compounds where R² is —CH₂OP(O)(OH)₂ may also find utility as prodrugs. In one embodiment of the compounds of formulas IIe, IIf, IIg, and IIh, Z is —CH—, R⁴ is H, a is 0, b is 1, R⁶ is 3′Cl, and R¹⁵ and R¹⁶ are H.

In another embodiment, R² is taken together with R³ to form —CH₂—O—CH₂— or —CH₂—CH₂—, which can be depicted as formulas IIi and IIj, respectively:

In another embodiment, R² and R³ are both —CH₃, which can be depicted as formula IIk:

In one embodiment of the compounds of formulas IIi, IIj, and IIk, R¹ is H, Z is —CH—, R⁴ is —C₁₋₈alkyl (e.g., —CH₂CH(CH₃)₂), a is 0, b is 1, and R⁶ is 3′Cl.

The Z group is selected from —CH— and —N—. These embodiments can be depicted as formulas IIIa and IIIb:

The R⁴ moiety is selected from:

H;

—C₁₋₈alkyl, e.g., —CH₃, —CH₂CH₃, —(CH₂)₂CH₃, —CH(CH₃)₂, —C(CH₃)₃, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₄CH₃, —(CH₂)₂CH(CH₃)₂, —(CH₂)₅CH₃, and —(CH₂)₆CH₃;

—C₁₋₃alkylene-O—C₁₋₈alkyl e.g., —(CH₂)₃—O—CH₂CH₃;

—C₁₋₃alkylene-C₆₋₁₀aryl, e.g., benzyl;

—C₁₋₃alkylene-O—C₆₋₁₀aryl, e.g., —(CH₂)₂—O-phenyl;

—C₁₋₃alkylene-C₁₋₉heteroaryl, e.g., —CH₂-pyridinyl and —(CH₂)₂-pyridinyl; —C₃₋₇cycloalkyl, e.g., cyclopentyl;

—[(CH₂)₂O]₁₋₃CH₃, e.g., —(CH₂)₂OCH₃ and —[(CH₂)₂O]₂CH₃; —C₁₋₆alkylene-OC(O)R⁴⁰, e.g., —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂CH(CH₃)OC(O)CH₂CH₃, —CH₂OC(O)OCH₃, —CH₂OC(O)OCH₂CH₃, —CH(CH₃)OC(O)OCH₂CH₃, —CH(CH₃)OC(O)O—CH(CH₃)₂, —CH₂CH(CH₃)OC(O)-cyclopentyl, —CH₂OC(O)O-cyclopropyl, —CH(CH₃)—OC(O)—O-cyclohexyl, —CH₂OC(O)O-cyclopentyl, —CH₂CH(CH₃)OC(O)-phenyl, —CH₂OC(O)O-phenyl, —CH₂OC(O)—CH[CH(CH₃)₂]—NH₂, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)OCH₃, and —CH(CH₃)OC(O)—CH(NH₂)CH₂COOCH₃;

—C₁₋₆alkylene-NR⁴¹R⁴², e.g., —(CH₂)₂—N(CH₃)₂,

—C₁₋₆alkylene-C(O)R⁴³, e.g., —CH₂C(O)OCH₃, —CH₂C(O)O-benzyl, —CH₂C(O)—N(CH₃)₂, and

—C₀₋₆alkylenemorpholine, e.g., —(CH₂)₂-morpholine and —(CH₂)₃-morpholine:

—C₁₋₆alkylene-SO₂—C₁₋₆alkyl, e.g., —(CH₂)₂SO₂CH₃;

The R⁴⁰ moiety is selected from:

—C₁₋₆alkyl, e.g., —CH₃ and —CH₂CH₃;

—O—C₁₋₆alkyl, e.g., —OCH₃, —O—CH₂CH₃, and —O—CH(CH₃)₂;

—C₃₋₇cycloalkyl, e.g., cyclopentyl;

—O—C₃₋₇cycloalkyl, e.g., —O-cyclopropyl, —O-cyclohexyl, and —O-cyclopentyl;

phenyl;

—O-phenyl;

—NR⁴¹R⁴²;

—CH(R⁴⁵)—NH₂, e.g., —CH[CH(CH₃)₂]—NH₂;

—CH(R⁴⁵)—NHC(O)O—C₁₋₆alkyl, e.g., —CH[CH(CH₃)₂]—NHC(O)OCH₃; and

—CH(NH₂)CH₂COOCH₃.

The R⁴¹ and R⁴² moieties are independently selected from H, —C₁₋₆alkyl (e.g., CH₃), and benzyl. Alternately, the R⁴¹ and R⁴² moieties can be taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—, for example to form a group such as:

The R⁴³ moiety is selected from —O—C₁₋₆alkyl, e.g., —OCH₃, —O-benzyl, and —NR⁴¹R⁴², e.g., —N(CH₃)₂, and

The R⁴⁴ moiety is —C₁₋₆alkyl (e.g., —CH₃ and —C(CH₃)₃) or —C₀₋₆alkylene-C₆₋₁₀aryl. The R⁴⁵ moiety is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl.

In addition, each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms. For example, when R⁴ is —C₁₋₈alkyl, R⁴ can also be a group such as —CH₂CF₃, —CH(CH₃)CF₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —CH₂CF₂CF₃, —CH(CF₃)₂, —CH(CH₂F)₂, —C(CF₃)₂CH₃, and —CH(CH₃)CF₂CF₃.

In one embodiment, R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, and

where R⁴⁴ is —C₁₋₆alkyl; and each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms. In one specific embodiment, R⁴ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —C(CH₃)₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —(CH₂)₃—O—CH₂CH₃, —(CH₂)₂—O-phenyl, —(CH₂)₂OCH₃, and

where R⁴⁴ is —CH₃. In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd.

In one embodiment, R¹ is H. In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd. In yet another embodiment, both R¹ and R⁴ are H.

In other embodiments these compounds have formulas IIa-IIh, IIm-IIo, IIIa-IIIb, and IVa-IVd. In another embodiment, R⁴ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd. In one aspect of the invention, these compounds may find particular utility as prodrugs or as intermediates in the synthetic procedures described herein. In one embodiment, both R¹ and R⁴ are such prodrug moieties. In another embodiment, one of R¹ and R⁴ is a prodrug moiety and the other is H. Specific examples of such prodrug moieties include where R⁴ is —C₁₋₆alkylene-OC(O)R¹⁰, such as —CH(CH₃)OC(O)—O-cyclohexyl:

making the compound a cilexetil ester; or R⁴ is —C₀₋₆alkylenemorpholine such as —(CH₂)₂— morpholine:

making the compound a 2-morpholinoethyl or mofetil ester; or

such as —CH₂-5-methyl-[1,3]dioxol-2-one:

making the compound a medoxomil ester.

The numbering for the R⁵ and R⁶ groups is as follows:

The integer “a” is 0 or 1. The R⁵ moiety, when present, is selected from halo, —CH₃, —CF₃, and —CN. In one embodiment, a is 0. In another embodiment, a is 1, and R⁵ is halo, such as 3-chloro or 3-fluoro. In yet another embodiment a is 0, or a is 1 and R⁵ is halo. In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd.

The integer “b” is 0 or an integer from 1 to 3. The R⁶ moiety, when present, is independently selected from halo, —OH, —CH₃, —OCH₃, —CN, and —CF₃. In one embodiment, b is 0. In another embodiment, b is 1 and R⁶ is selected from Cl, F, —OH, —CH₃, —OCH₃, —CN, and —CF₃, such 2′-chloro, 3′-chloro, 2′-fluoro, 3′-fluoro, 2′-hydroxy, 3′-hydroxy, 3′-methyl, 2′-methoxy, 3′-cyano, or 3′-trifluoromethyl. In another embodiment, b is 1 and R⁶ is halo, —CH₃, or —OCH₃, such 3′-chloro, 3′-methyl, or 2′-methoxy. In another embodiment, b is 2 and R⁶ is 2′-fluoro-5′-chloro, 2′,5′-dichloro, 2′,5′-difluoro, 2′-methyl-5′-chloro, 3′-fluoro-5′-chloro, 3′-hydroxy-5′-chloro, 3′,5′-dichloro, 3′,5′-difluoro, 2′-methoxy-5′-chloro, 2′-methoxy-5′-fluoro, 2′-hydroxy-5′-fluoro, 2′-fluoro-3′-chloro, 2′-hydroxy-5′-chloro, or 2′-hydroxy-3′-chloro. In another embodiment, b is 3 and each R⁶ is independently halo or —CH₃, such as 2′-methyl-3′,5′-dichloro or 2′-fluoro-3′-methyl-5′-chloro. In one particular embodiment, b is 0, or b is 1 and R⁶ is halo, or b is 2 and each R⁶ is independently selected from halo and —CH₃. In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd.

In other exemplary embodiments, a is 0 and b is 0; or a is 0, b is 1, and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro; or a is 0, b is 2, and R⁶ is 2′-fluoro, 5′-chloro or 2′-methyl, 5′-chloro or 2′,5′-dichloro; a is 1, R⁵ is 3-chloro, and b is 0; or a is 1, R⁵ is 3-chloro, b is 1, and R⁶ is 3′-chloro; or a is 1, R⁵ is 3-chloro, b is 2, and R⁶ is 2′-fluoro, 5′-chloro. In other embodiments these compounds have formulas IIa-IIk, IIIa-IIIb, and IVa-IVd. Of particular interest are compounds of the formulas:

The methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl. For example, in one embodiment, the methylene linker on the biphenyl is unsubstituted; in another embodiment, the methylene linker on the biphenyl is substituted with one —C₁₋₆alkyl group (e.g., —CH₃); and in yet another embodiment, the methylene linker on the biphenyl is substituted with two —C₁₋₆alkyl groups (e.g., two —CH₃ groups); in another embodiment, the methylene linker on the biphenyl is substituted with a cyclopropyl group. These embodiments are depicted, respectively, as formulas IVa-IVd:

In one embodiment of the compounds of formulas IVa, IVb, IVc, and IVd, R¹ is H, R² is —OR²¹ and R²¹ is H, R³ is H, Z is —CH—, R⁴ is —C₁₋₈alkyl (e.g., —CH₂CH(CH₃)₂), a is 0, b is 1, and R⁶ is 3′Cl.

In another embodiment, R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₆alkylene-OC(O)R¹⁰, and

where R¹⁰ is —C₁₋₆alkyl, —O—C₁₋₆alkyl, or —CH[R¹⁵]—NHC(O)O—C₁₋₆alkyl; R¹⁴ is —C₁₋₆alkyl; R¹⁵ is —CH(CH₃)₂; and each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms;

R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, and

where R⁴⁴ is —C₁₋₆alkyl; and each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms;

a is 0 and b is 0; or a is 0, b is 1, and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro; or a is 0, b is 2, and R⁶ is 2′-fluoro, 5′-chloro or 2′-methyl, 5′-chloro or 2′,5′-dichloro; or a is 1, R⁵ is 3-chloro, and b is 0; or a is 1, R⁵ is 3-chloro, b is 1, and R⁶ is 3′-chloro; or a is 1, R⁵ is 3-chloro, b is 2, and R⁶ is 2′-fluoro, 5′-chloro; and where the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups. In one particular embodiment of these compounds, R² is —OR²¹ or —CH₂OR²¹; and R³ is H or —CH₃; where R²¹ is H.

In addition, particular compounds of formula I that are of interest include those set forth in the Examples below, as well as pharmaceutically acceptable salts thereof.

General Synthetic Procedures

Compounds of the invention can be prepared from readily available starting materials using the following general methods, the procedures set forth in the Examples, or by using other methods, reagents, and starting materials that are known to those of ordinary skill in the art. Although the following procedures may illustrate a particular embodiment of the invention, it is understood that other embodiments of the invention can be similarly prepared using the same or similar methods or by using other methods, reagents and starting materials known to those of ordinary skill in the art. It will also be appreciated that where typical or preferred process conditions (for example, reaction temperatures, times, mole ratios of reactants, solvents, pressures, etc.) are given, other process conditions can also be used unless otherwise stated. In some instances, reactions were conducted at room temperature and no actual temperature measurement was taken. It is understood that room temperature can be taken to mean a temperature within the range commonly associated with the ambient temperature in a laboratory environment, and will typically be in the range of about 18° C. to about 30° C. In other instances, reactions were conducted at room temperature and the temperature was actually measured and recorded. While optimum reaction conditions will typically vary depending on various reaction parameters such as the particular reactants, solvents and quantities used, those of ordinary skill in the art can readily determine suitable reaction conditions using routine optimization procedures.

Additionally, as will be apparent to those skilled in the art, conventional protecting groups may be necessary or desired to prevent certain functional groups from undergoing undesired reactions. The choice of a suitable protecting group for a particular functional group as well as suitable conditions and reagents for protection and deprotection of such functional groups are well-known in the art. Protecting groups other than those illustrated in the procedures described herein may be used, if desired. For example, numerous protecting groups, and their introduction and removal, are described in T. W. Greene and G. M. Wuts, Protecting Groups in Organic Synthesis, Fourth Edition, Wiley, New York, 2006, and references cited therein.

Carboxy-protecting groups are suitable for preventing undesired reactions at a carboxy group, and examples include, but are not limited to, methyl, ethyl, t-butyl, benzyl (Bn), p-methoxybenzyl (PMB), 9-fluorenylmethyl (Fm), trimethylsilyl (TMS), t-butyldimethylsilyl (TBDMS), diphenylmethyl (benzhydryl, DPM) and the like. Amino-protecting groups are suitable for preventing undesired reactions at an amino group, and examples include, but are not limited to, t-butoxycarbonyl (BOC), trityl (Tr), benzyloxycarbonyl (Cbz), 9-fluorenylmethoxycarbonyl (Fmoc), formyl, trimethylsilyl (TMS), t-butyldimethylsilyl (TBDMS), and the like. Hydroxyl-protecting groups are suitable for preventing undesired reactions at a hydroxyl group, and examples include, but are not limited to C₁₋₆alkyls, silyl groups including triC₁₋₆alkylsilyl groups, such as trimethylsilyl (TMS), triethylsilyl (TES), and t-butyldimethylsilyl (TBDMS); esters (acyl groups) including C₁₋₆alkanoyl groups, such as formyl, acetyl, and pivaloyl, and aromatic acyl groups such as benzoyl; arylmethyl groups such as benzyl (Bn), p-methoxybenzyl (PMB), 9-fluorenylmethyl (Fm), and diphenylmethyl (benzhydryl, DPM); and the like.

Standard deprotection techniques and reagents are used to remove the protecting groups, and may vary depending upon which group is used. For example, sodium or lithium hydroxide is commonly used when the carboxy-protecting group is methyl, an acid such as TFA or HCl is commonly used when the carboxy-protecting group is ethyl or t-butyl, and H₂/Pd/C may be used when the carboxy-protecting group is benzyl. A BOC amino-protecting group can be removed using an acidic reagent such as TFA in DCM or HCl in 1,4-dioxane, while a Cbz amino-protecting group can be removed by employing catalytic hydrogenation conditions such as H₂ (1 atm) and 10% Pd/C in an alcoholic solvent (“H₂/Pd/C”). H₂/Pd/C is commonly used when the hydroxyl-protecting group is benzyl, while NaOH is commonly used when the hydroxyl-protecting group is an acyl group.

Suitable bases for use in these schemes include, by way of illustration and not limitation, potassium carbonate, calcium carbonate, sodium carbonate, triethylamine, pyridine, 1,8-diazabicyclo-[5.4.0]undec-7-ene (DBU), N,N-diisopropylethylamine (DIPEA), 4-methylmorpholine, sodium hydroxide, potassium hydroxide, potassium t-butoxide, and metal hydrides.

Suitable inert diluents or solvents for use in these schemes include, by way of illustration and not limitation, tetrahydrofuran (THF), acetonitrile (MeCN), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), dimethyl sulfoxide (DMSO), toluene, dichloromethane (DCM), chloroform (CHCl₃), carbon tetrachloride (CCl₄), 1,4-dioxane, methanol, ethanol, water, and the like.

Suitable carboxylic acid/amine coupling reagents include benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluorophosphate (BOP), benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), N,N,N′,N′-tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (HATU), (2-(6-chloro-1H-benzotriazole-1-yl)-1,1,3,3-tetramethylaminium hexafluorophosphate) (HCTU), 1,3-dicyclohexylcarbodiimide (DCC), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDCI), carbonyldiimidazole (CDI), 1-hydroxybenzotriazole (HOBt), and the like. Coupling reactions are conducted in an inert diluent in the presence of a base such as DIPEA, and are performed under conventional amide bond-forming conditions.

All reactions are typically conducted at a temperature within the range of about −78 C to 100° C., for example at room temperature. Reactions may be monitored by use of thin layer chromatography (TLC), high performance liquid chromatography (HPLC), and/or LCMS until completion. Reactions may be complete in minutes, or may take hours, typically from 1-2 hours and up to 48 hours. Upon completion, the resulting mixture or reaction product may be further treated in order to obtain the desired product. For example, the resulting mixture or reaction product may be subjected to one or more of the following procedures: concentrating or partitioning (for example, between EtOAc and water or between 5% THF in EtOAc and 1M phosphoric acid); extraction (for example, with EtOAc, CHCl₃, DCM, chloroform); washing (for example, with saturated aqueous NaCl, saturated aqueous NaHCO₃, Na₂CO₃ (5%), CHCl₃ or 1M NaOH); drying (for example, over MgSO₄, over Na₂SO₄, or in vacuo); filtering; crystallizing (for example, from EtOAc and hexanes); being concentrated (for example, in vacuo); and/or purification (e.g., silica gel chromatography, flash chromatography, preparative HPLC, reverse phase-HPLC, or crystallization).

Compounds of formula I, as well as their salts, can be prepared as shown in Scheme I:

The process comprises the step of coupling compound 1 with compound 2, where R¹-R⁶, Z, a, and b are as defined for formula I, and P is selected from H and a suitable amino-protecting group, examples of which include t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl. When P is an amino protecting group, the process further comprises deprotecting the compound of formula 1, before or in situ with the coupling step.

In instances where R¹ is a group such as —OCH₃ or —OCH₂CH₃, the coupling step may be followed by a deprotection step to provide a compound of formula I where R¹ is a group such as —OH. Thus, one method of preparing compounds of the invention involves coupling compounds 1 and 2, with an optional deprotection step to form a compound of formula I or a pharmaceutically acceptable salt thereof.

Methods of preparing compound 1 are described in the Examples. Compound 2 is generally commercially available or can be prepared using procedures that are known in the art.

Certain intermediates described herein are believed to be novel and accordingly, such compounds are provided as further aspects of the invention including, for example, the compounds of formula 1, or a salt thereof:

where P is H or a suitable amino-protecting group, examples of which include, t-butoxycarbonyl, trityl, benzyloxycarbonyl, 9-fluorenylmethoxycarbonyl, formyl, trimethylsilyl, and t-butyldimethylsilyl; and R¹, R², R³, R⁵, R⁶, Z, a and b are as defined for formula I.

Further details regarding specific reaction conditions and other procedures for preparing representative compounds of the invention or intermediates thereof are described in the Examples set forth below.

Utility

Compounds of the invention possess neprilysin (NEP) inhibition activity, that is, the compounds are able to inhibit enzyme-catalytic activity. In another embodiment, the compounds do not exhibit significant inhibitory activity of the angiotensin-converting enzyme. One measure of the ability of a compound to inhibit NEP activity is the inhibition constant (pK_(i)). The pK_(i) value is the negative logarithm to base 10 of the dissociation constant (K_(i)), which is typically reported in molar units. Compounds of the invention of particular interest are those having a pK_(i) at NEP greater than or equal to 6.0, particularly those having a pK_(i) greater than or equal to 7.0, and even more particularly those having a pK_(i) greater than or equal to 8.0. In one embodiment, compounds of interest have a pK_(i) in the range of 6.0-6.9; in another embodiment, compounds of interest have a pK_(i) in the range of 7.0-7.9; in yet another embodiment, compounds of interest have a pK_(i) in the range of 8.0-8.9; and in still another embodiment, compounds of interest have a pK_(i) in the range of greater than or equal to 9.0. Such values can be determined by techniques that are well known in the art, as well as in the assays described herein.

Another measure of the ability of a compound to inhibit NEP activity is the apparent inhibition constant (IC₅₀), which is the molar concentration of compound that results in half-maximal inhibition of substrate conversion by the NEP enzyme. The pIC₅₀ value is the negative logarithm to base 10 of the IC₅₀. Compounds of the invention that are of particular interest, include those that exhibit a pIC₅₀ for NEP greater than or equal to about 5.0. Compounds of interest also include those having a pIC₅₀ for NEP≧about 6.0 or a pIC₅₀ for NEP≧about 7.0. In another embodiment, compounds of interest have a pIC₅₀ for NEP within the range of about 7.0-11.0; and in another embodiment, within the range of about 8.0-11.0, such as within the range of about 8.0-10.0.

It is noted that in some cases, compounds of the invention may possess weak NEP inhibition activity. In such cases, those of skill in the art will recognize that these compounds still have utility as research tools.

Exemplary assays to determine properties of compounds of the invention, such as the NEP inhibiting activity, are described in the Examples and include by way of illustration and not limitation, assays that measure NEP inhibition (described in Assay 1). Useful secondary assays include assays to measure ACE inhibition (also described in Assay 1) and aminopeptidase P (APP) inhibition (described in Sulpizio et al. (2005) JPET 315:1306-1313). A pharmacodynamic assay to assess the in vivo inhibitory potencies for ACE and NEP in anesthetized rats is described in Assay 2 (see also Seymour et al. (1985) Hypertension 7(Suppl I):I-35-I-42 and Wigle et al. (1992) Can. J. Physiol. Pharmacol. 70:1525-1528), where ACE inhibition is measured as the percent inhibition of the angiotensin I pressor response and NEP inhibition is measured as increased urinary cyclic guanosine 3′,5′-monophosphate (cGMP) output.

There are many in vivo assays that can be used to ascertain further utilities of the compounds of the invention. The conscious spontaneously hypertensive rat (SHR) model is a renin dependent hypertension model, and is described in Assay 3. See also Intengan et al. (1999) Circulation 100(22):2267-2275 and Badyal et al. (2003) Indian Journal of Pharmacology 35:349-362. The conscious desoxycorticosterone acetate-salt (DOCA-salt) rat model is a volume dependent hypertension model that is useful for measuring NEP activity, and is described in Assay 4. See also Trapani et al. (1989) J. Cardiovasc. Pharmacol. 14:419-424, Intengan et al. (1999) Hypertension 34(4):907-913, and Badyal et al. (2003) supra). The DOCA-salt model is particularly useful for evaluating the ability of a test compound to reduce blood pressure as well as to measure a test compound's ability to prevent or delay a rise in blood pressure. The Dahl salt-sensive (DSS) hypertensive rat model is a model of hypertension that is sensitive to dietary salt (NaCl), and is described in Assay 5. See also Rapp (1982) Hypertension 4:753-763. The rat monocrotaline model of pulmonary arterial hypertension described, for example, in Kato et al. (2008) J. Cardiovasc. Pharmacol. 51(1):18-23, is a reliable predictor of clinical efficacy for the treatment of pulmonary arterial hypertension. Heart failure animal models include the DSS rat model for heart failure and the aorto-caval fistula model (AV shunt), the latter of which is described, for example, in Norling et al. (1996) J. Amer. Soc. Nephrol. 7:1038-1044. Other animal models, such as the hot plate, tail-flick and formalin tests, can be used to measure the analgesic properties of compounds of the invention, as well as the spinal nerve ligation (SNL) model of neuropathic pain. See, for example, Malmberg et al. (1999) Current Protocols in Neuroscience 8.9.1-8.9.15.

Compounds of the invention are expected to inhibit the NEP enzyme in any of the assays listed above, or assays of a similar nature. Thus, the aforementioned assays are useful in determining the therapeutic utility of compounds of the invention, for example, their utility as antihypertensive agents or antidiarrheal agents. Other properties and utilities of compounds of the invention can be demonstrated using other in vitro and in vivo assays well-known to those skilled in the art. Compounds of formula I may be active drugs as well as prodrugs. Thus, when discussing the activity of compounds of the invention, it is understood that any such prodrugs may not exhibit the expected activity in an assay, but are expected to exhibit the desired activity once metabolized.

Compounds of the invention are expected to be useful for the treatment and/or prevention of medical conditions responsive to NEP inhibition. Thus it is expected that patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme or by increasing the levels of its peptide substrates, can be treated by administering a therapeutically effective amount of a compound of the invention. For example, by inhibiting NEP, the compounds are expected to potentiate the biological effects of endogenous peptides that are metabolized by NEP, such as the natriuretic peptides, bombesin, bradykinins, calcitonin, endothelins, enkephalins, neurotensin, substance P and vasoactive intestinal peptide. Thus, these compounds are expected to have other physiological actions, for example, on the renal, central nervous, reproductive and gastrointestinal systems.

In one embodiment of the invention, patients suffering from a disease or disorder that is treated by inhibiting the NEP enzyme, are treated by administering a compound of the invention that is in its active form, i.e., a compound of formula I where R¹ and R⁴ are H, and R², R³, R⁵, R⁶, a, b, and Z are as defined for formula I.

In another embodiment, patients are treated by administering a compound that is metabolized in vitro to form a compound of formula I where R¹ and R⁴ are H, and R², R², R³, R⁵, R⁶, a, b, and Z are as defined for formula I.

In another embodiment, patients are treated by administering a compound of the invention that is in its prodrug form at the R¹ group, i.e., a compound of formula I where R¹ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In yet another embodiment, patients are treated by administering a compound of the invention that is in its prodrug form at the R⁴ group, i.e., a compound of formula I where R⁴ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

In still another embodiment, patients are treated by administering a compound of the invention that is in its prodrug form at the R¹ group and at the R⁴ group.

Cardiovascular Diseases

By potentiating the effects of vasoactive peptides like the natriuretic peptides and bradykinin, compounds of the invention are expected to find utility in treating and/or preventing medical conditions such as cardiovascular diseases. See, for example, Roques et al. (1993) Pharmacol. Rev. 45:87-146 and Dempsey et al. (2009) Amer. J. of Pathology 174(3):782-796. Cardiovascular diseases of particular interest include hypertension and heart failure. Hypertension includes, by way of illustration and not limitation: primary hypertension, which is also referred to as essential hypertension or idiopathic hypertension; secondary hypertension; hypertension with accompanying renal disease; severe hypertension with or without accompanying renal disease; pulmonary hypertension, including pulmonary arterial hypertension; and resistant hypertension. Heart failure includes, by way of illustration and not limitation: congestive heart failure; acute heart failure; chronic heart failure, for example with reduced left ventricular ejection fraction (also referred to as systolic heart failure) or with preserved left ventricular ejection fraction (also referred to as diastolic heart failure); and acute and chronic decompensated heart failure, with or without accompanying renal disease. Thus, one embodiment of the invention relates to a method for treating hypertension, particularly primary hypertension or pulmonary arterial hypertension, comprising administering to a patient a therapeutically effective amount of a compound of the invention.

For treatment of primary hypertension, the therapeutically effective amount is typically the amount that is sufficient to lower the patient's blood pressure. This would include both mild-to-moderate hypertension and severe hypertension. When used to treat hypertension, the compound may be administered in combination with other therapeutic agents such as aldosterone antagonists, aldosterone synthase inhibitors, angiotensin-converting enzyme inhibitors and dual-acting angiotensin-converting enzyme/neprilysin inhibitors, angiotensin-converting enzyme 2 (ACE2) activators and stimulators, angiotensin-II vaccines, anti-diabetic agents, anti-lipid agents, anti-thrombotic agents, AT₁ receptor antagonists and dual-acting AT₁ receptor antagonist/neprilysin inhibitors, β₁-adrenergic receptor antagonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, calcium channel blockers, diuretics, endothelin receptor antagonists, endothelin converting enzyme inhibitors, neprilysin inhibitors, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, nitric oxide donors, non-steroidal anti-inflammatory agents, phosphodiesterase inhibitors (specifically PDE-V inhibitors), prostaglandin receptor agonists, renin inhibitors, soluble guanylate cyclase stimulators and activators, and combinations thereof. In one particular embodiment of the invention, a compound of the invention is combined with an AT₁ receptor antagonist, a calcium channel blocker, a diuretic, or a combination thereof, and used to treat primary hypertension. In another particular embodiment of the invention, a compound of the invention is combined with an AT₁ receptor antagonist, and used to treat hypertension with accompanying renal disease. When used to treat resistant hypertension, the compound may be administered in combination with other therapeutic agents such as aldosterone synthase inhibitors.

For treatment of pulmonary arterial hypertension, the therapeutically effective amount is typically the amount that is sufficient to lower the pulmonary vascular resistance. Other goals of therapy are to improve a patient's exercise capacity. For example, in a clinical setting, the therapeutically effective amount can be the amount that improves a patient's ability to walk comfortably for a period of 6 minutes (covering a distance of approximately 20-40 meters). When used to treat pulmonary arterial hypertension the compound may be administered in combination with other therapeutic agents such as α-adrenergic receptor antagonists, β₁-adrenergic receptor antagonists, β₂-adrenergic receptor agonists, angiotensin-converting enzyme inhibitors, anticoagulants, calcium channel blockers, diuretics, endothelin receptor antagonists, PDE-V inhibitors, prostaglandin analogs, selective serotonin reuptake inhibitors, and combinations thereof. In one particular embodiment of the invention, a compound of the invention is combined with a PDE-V inhibitor or a selective serotonin reuptake inhibitor and used to treat pulmonary arterial hypertension.

Another embodiment of the invention relates to a method for treating heart failure, in particular congestive heart failure (including both systolic and diastolic congestive heart failure), comprising administering to a patient a therapeutically effective amount of a compound of the invention. Typically, the therapeutically effective amount is the amount that is sufficient to lower blood pressure and/or improve renal functions. In a clinical setting, the therapeutically effective amount can be the amount that is sufficient to improve cardiac hemodynamics, like for instance reduction in wedge pressure, right atrial pressure, filling pressure, and vascular resistance. In one embodiment, the compound is administered as an intravenous dosage form. When used to treat heart failure, the compound may be administered in combination with other therapeutic agents such as adenosine receptor antagonists, advanced glycation end product breakers, aldosterone antagonists, AT₁ receptor antagonists, β-adrenergic receptor antagonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, chymase inhibitors, digoxin, diuretics, endothelin converting enzyme (ECE) inhibitors, endothelin receptor antagonists, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, nitric oxide donors, prostaglandin analogs, PDE-V inhibitors, soluble guanylate cyclase activators and stimulators, and vasopressin receptor antagonists. In one particular embodiment of the invention, a compound of the invention is combined with an aldosterone antagonist, a β₁-adrenergic receptor antagonist, an AT₁ receptor antagonist, or a diuretic, and used to treat congestive heart failure.

Diarrhea

As NEP inhibitors, compounds of the invention are expected to inhibit the degradation of endogenous enkephalins and thus such compounds may also find utility for the treatment of diarrhea, including infectious and secretory/watery diarrhea. See, for example, Baumer et al. (1992) Gut 33:753-758; Farthing (2006) Digestive Diseases 24:47-58; and Marçais-Collado (1987) Eur. J. Pharmacol. 144(2):125-132. When used to treat diarrhea, compounds of the invention may be combined with one or more additional antidiarrheal agents.

Renal Diseases

By potentiating the effects of vasoactive peptides like the natriuretic peptides and bradykinin, compounds of the invention are expected to enhance renal function (see Chen et al. (1999) Circulation 100:2443-2448; Lipkin et al. (1997) Kidney Int. 52:792-801; and Dussaule et al. (1993) Clin. Sci. 84:31-39) and find utility in treating and/or preventing renal diseases. Renal diseases of particular interest include diabetic nephropathy, chronic kidney disease, proteinuria, and particularly acute kidney injury or acute renal failure (see Sharkovska et al. (2011) Clin. Lab. 57:507-515 and Newaz et al. (2010) Renal Failure 32:384-390). When used to treat renal disease, the compound may be administered in combination with other therapeutic agents such as angiotensin-converting enzyme inhibitors, AT₁ receptor antagonists, and diuretics.

Preventative Therapy

By potentiating the effects of the natriuretic peptides, compounds of the invention are also expected to be useful in preventative therapy, due to the antihypertrophic and antifibrotic effects of the natriuretic peptides (see Potter et al. (2009) Handbook of Experimental Pharmacology 191:341-366), for example in preventing the progression of cardiac insufficiency after myocardial infarction, preventing arterial restenosis after angioplasty, preventing thickening of blood vessel walls after vascular operations, preventing atherosclerosis, and preventing diabetic angiopathy.

Glaucoma

By potentiating the effects of the natriuretic peptides, compounds of the invention are expected to be useful to treat glaucoma. See, for example, Diestelhorst et al. (1989) International Ophthalmology 12:99-101. When used to treat glaucoma, compounds of the invention may be combined with one or more additional antiglaucoma agents.

Pain Relief

As NEP inhibitors, compounds of the invention are expected to inhibit the degradation of endogenous enkephalins and thus such compounds may also find utility as analgesics. See, for example, Roques et al. (1980) Nature 288:286-288 and Thanawala et al. (2008) Current Drug Targets 9:887-894. When used to treat pain, the compounds of the invention may be combined with one or more additional antinociceptive drugs such as aminopeptidase N or dipeptidyl peptidase III inhibitors, non-steroidal anti-inflammatory agents, monoamine reuptake inhibitors, muscle relaxants, NMDA receptor antagonists, opioid receptor agonists, 5-HT_(1D) serotonin receptor agonists, and tricyclic antidepressants.

Other Utilities

Due to their NEP inhibition properties, compounds of the invention are also expected to be useful as antitussive agents, as well as find utility in the treatment of portal hypertension associated with liver cirrhosis (see Sansoe et al. (2005) J. Hepatol. 43:791-798), cancer (see Vesely (2005) J. Investigative Med. 53:360-365), depression (see Noble et al. (2007) Exp. Opin. Ther. Targets 11:145-159), menstrual disorders, preterm labor, pre-eclampsia, endometriosis, reproductive disorders (for example, male and female infertility, polycystic ovarian syndrome, implantation failure), and male and female sexual dysfunction, including male erectile dysfunction and female sexual arousal disorder. More specifically, the compounds of the invention are expected to be useful in treating female sexual dysfunction (see Pryde et al. (2006) J. Med. Chem. 49:4409-4424), which is often defined as a female patient's difficulty or inability to find satisfaction in sexual expression. This covers a variety of diverse female sexual disorders including, by way of illustration and not limitation, hypoactive sexual desire disorder, sexual arousal disorder, orgasmic disorder and sexual pain disorder. When used to treat such disorders, especially female sexual dysfunction, compounds of the invention may be combined with one or more of the following secondary agents: PDE-V inhibitors, dopamine agonists, estrogen receptor agonists and/or antagonists, androgens, and estrogens. Due to their NEP inhibition properties, compounds of the invention are also expected to have anti-inflammatory properties, and are expected to have utility as such, particularly when used in combination with statins.

Recent studies suggest that NEP plays a role in regulating nerve function in insulin-deficient diabetes and diet induced obesity. Coppey et al. (2011) Neuropharmacology 60:259-266. Therefore, due to their NEP inhibition properties, compounds of the invention are also expected to be useful in providing protection from nerve impairment caused by diabetes or diet induced obesity.

The amount of the compound of the invention administered per dose or the total amount administered per day may be predetermined or it may be determined on an individual patient basis by taking into consideration numerous factors, including the nature and severity of the patient's condition, the condition being treated, the age, weight, and general health of the patient, the tolerance of the patient to the active agent, the route of administration, pharmacological considerations such as the activity, efficacy, pharmacokinetics and toxicology profiles of the compound and any secondary agents being administered, and the like. Treatment of a patient suffering from a disease or medical condition (such as hypertension) can begin with a predetermined dosage or a dosage determined by the treating physician, and will continue for a period of time necessary to prevent, ameliorate, suppress, or alleviate the symptoms of the disease or medical condition. Patients undergoing such treatment will typically be monitored on a routine basis to determine the effectiveness of therapy. For example, in treating hypertension, blood pressure measurements may be used to determine the effectiveness of treatment. Similar indicators for other diseases and conditions described herein, are well known and are readily available to the treating physician. Continuous monitoring by the physician will insure that the optimal amount of the compound of the invention will be administered at any given time, as well as facilitating the determination of the duration of treatment. This is of particular value when secondary agents are also being administered, as their selection, dosage, and duration of therapy may also require adjustment. In this way, the treatment regimen and dosing schedule can be adjusted over the course of therapy so that the lowest amount of active agent that exhibits the desired effectiveness is administered and, further, that administration is continued only so long as is necessary to successfully treat the disease or medical condition.

Research Tools

Since compounds of the invention possess NEP enzyme inhibition activity, such compounds are also useful as research tools for investigating or studying biological systems or samples having a NEP enzyme, for example to study diseases where the NEP enzyme or its peptide substrates plays a role. Any suitable biological system or sample having a NEP enzyme may be employed in such studies which may be conducted either in vitro or in vivo. Representative biological systems or samples suitable for such studies include, but are not limited to, cells, cellular extracts, plasma membranes, tissue samples, isolated organs, mammals (such as mice, rats, guinea pigs, rabbits, dogs, pigs, humans, and so forth), and the like, with mammals being of particular interest. In one particular embodiment of the invention, NEP enzyme activity in a mammal is inhibited by administering a NEP-inhibiting amount of a compound of the invention. Compounds of the invention can also be used as research tools by conducting biological assays using such compounds.

When used as a research tool, a biological system or sample comprising a NEP enzyme is typically contacted with a NEP enzyme-inhibiting amount of a compound of the invention. After the biological system or sample is exposed to the compound, the effects of inhibiting the NEP enzyme are determined using conventional procedures and equipment, such as by measuring receptor binding in a binding assay or measuring ligand-mediated changes in a functional assay. Exposure encompasses contacting cells or tissue with the compound, administering the compound to a mammal, for example by i.p., p.o, i.v., s.c., or inhaled administration, and so forth. This determining step can involve measuring a response (a quantitative analysis) or can involve making an observation (a qualitative analysis). Measuring a response involves, for example, determining the effects of the compound on the biological system or sample using conventional procedures and equipment, such as enzyme activity assays and measuring enzyme substrate or product mediated changes in functional assays. The assay results can be used to determine the activity level as well as the amount of compound necessary to achieve the desired result, that is, a NEP enzyme-inhibiting amount. Typically, the determining step will involve determining the effects of inhibiting the NEP enzyme.

Additionally, compounds of the invention can be used as research tools for evaluating other chemical compounds, and thus are also useful in screening assays to discover, for example, new compounds having NEP-inhibiting activity. In this manner, a compound of the invention is used as a standard in an assay to allow comparison of the results obtained with a test compound and with compounds of the invention to identify those test compounds that have about equal or superior activity, if any. For example, pK_(i) data for a test compound or a group of test compounds is compared to the pK_(i) data for a compound of the invention to identify those test compounds that have the desired properties, for example, test compounds having a pK_(i) value about equal or superior to a compound of the invention, if any. This aspect of the invention includes, as separate embodiments, both the generation of comparison data (using the appropriate assays) and the analysis of test data to identify test compounds of interest. Thus, a test compound can be evaluated in a biological assay, by a method comprising the steps of: (a) conducting a biological assay with a test compound to provide a first assay value; (b) conducting the biological assay with a compound of the invention to provide a second assay value; wherein step (a) is conducted either before, after or concurrently with step (b); and (c) comparing the first assay value from step (a) with the second assay value from step (b). Exemplary biological assays include a NEP enzyme inhibition assay.

Pharmaceutical Compositions and Formulations

Compounds of the invention are typically administered to a patient in the form of a pharmaceutical composition or formulation. Such pharmaceutical compositions may be administered to the patient by any acceptable route of administration including, but not limited to, oral, rectal, vaginal, nasal, inhaled, topical (including transdermal), ocular, and parenteral modes of administration. Further, the compounds of the invention may be administered, for example orally, in multiple doses per day (for example, two, three, or four times daily), in a single daily dose or a single weekly dose. It will be understood that any form of the compounds of the invention, (that is, free base, free acid, pharmaceutically acceptable salt, solvate, etc.) that is suitable for the particular mode of administration can be used in the pharmaceutical compositions discussed herein.

Accordingly, in one embodiment, the invention relates to a pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound of the invention. The compositions may contain other therapeutic and/or formulating agents if desired. When discussing compositions, the “compound of the invention” may also be referred to herein as the “active agent,” to distinguish it from other components of the formulation, such as the carrier. Thus, it is understood that the term “active agent” includes compounds of formula I as well as pharmaceutically acceptable salts, solvates and prodrugs of that compound.

The pharmaceutical compositions of the invention typically contain a therapeutically effective amount of a compound of the invention. Those skilled in the art will recognize, however, that a pharmaceutical composition may contain more than a therapeutically effective amount, such as in bulk compositions, or less than a therapeutically effective amount, that is, individual unit doses designed for multiple administration to achieve a therapeutically effective amount. Typically, the composition will contain from about 0.01-95 wt % of active agent, including, from about 0.01-30 wt %, such as from about 0.01-10 wt %, with the actual amount depending upon the formulation itself, the route of administration, the frequency of dosing, and so forth. In one embodiment, a composition suitable for an oral dosage form, for example, may contain about 5-70 wt %, or from about 10-60 wt % of active agent.

Any conventional carrier or excipient may be used in the pharmaceutical compositions of the invention. The choice of a particular carrier or excipient, or combinations of carriers or excipients, will depend on the mode of administration being used to treat a particular patient or type of medical condition or disease state. In this regard, the preparation of a suitable composition for a particular mode of administration is well within the scope of those skilled in the pharmaceutical arts. Additionally, carriers or excipients used in such compositions are commercially available. By way of further illustration, conventional formulation techniques are described in Remington: The Science and Practice of Pharmacy, 20^(th) Edition, Lippincott Williams & White, Baltimore, Md. (2000); and H. C. Ansel et al., Pharmaceutical Dosage Forms and Drug Delivery Systems, 7^(th) Edition, Lippincott Williams & White, Baltimore, Md. (1999).

Representative examples of materials which can serve as pharmaceutically acceptable carriers include, but are not limited to, the following: sugars, such as lactose, glucose and sucrose; starches, such as corn starch and potato starch; cellulose, such as microcrystalline cellulose, and its derivatives, such as sodium carboxymethyl cellulose, ethyl cellulose and cellulose acetate; powdered tragacanth; malt; gelatin; talc; excipients, such as cocoa butter and suppository waxes; oils, such as peanut oil, cottonseed oil, safflower oil, sesame oil, olive oil, corn oil and soybean oil; glycols, such as propylene glycol; polyols, such as glycerin, sorbitol, mannitol and polyethylene glycol; esters, such as ethyl oleate and ethyl laurate; agar; buffering agents, such as magnesium hydroxide and aluminum hydroxide; alginic acid; pyrogen-free water; isotonic saline; Ringer's solution; ethyl alcohol; phosphate buffer solutions; compressed propellant gases, such as chlorofluorocarbons and hydrofluorocarbons; and other non-toxic compatible substances employed in pharmaceutical compositions.

Pharmaceutical compositions are typically prepared by thoroughly and intimately mixing or blending the active agent with a pharmaceutically acceptable carrier and one or more optional ingredients. The resulting uniformly blended mixture may then be shaped or loaded into tablets, capsules, pills, canisters, cartridges, dispensers and the like using conventional procedures and equipment.

In one embodiment, the pharmaceutical compositions are suitable for oral administration. Suitable compositions for oral administration may be in the form of capsules, tablets, pills, lozenges, cachets, dragees, powders, granules; solutions or suspensions in an aqueous or non-aqueous liquid; oil-in-water or water-in-oil liquid emulsions; elixirs or syrups; and the like; each containing a predetermined amount of the active agent.

When intended for oral administration in a solid dosage form (capsules, tablets, pills and the like), the composition will typically comprise the active agent and one or more pharmaceutically acceptable carriers, such as sodium citrate or dicalcium phosphate. Solid dosage forms may also comprise: fillers or extenders, such as starches, microcrystalline cellulose, lactose, sucrose, glucose, mannitol, and/or silicic acid; binders, such as carboxymethylcellulose, alginates, gelatin, polyvinyl pyrrolidone, sucrose and/or acacia; humectants, such as glycerol; disintegrating agents, such as agar-agar, calcium carbonate, potato or tapioca starch, alginic acid, certain silicates, and/or sodium carbonate; solution retarding agents, such as paraffin; absorption accelerators, such as quaternary ammonium compounds; wetting agents, such as cetyl alcohol and/or glycerol monostearate; absorbents, such as kaolin and/or bentonite clay; lubricants, such as talc, calcium stearate, magnesium stearate, solid polyethylene glycols, sodium lauryl sulfate, and/or mixtures thereof; coloring agents; and buffering agents.

Release agents, wetting agents, coating agents, sweetening, flavoring and perfuming agents, preservatives and antioxidants may also be present in the pharmaceutical compositions. Exemplary coating agents for tablets, capsules, pills and like, include those used for enteric coatings, such as cellulose acetate phthalate, polyvinyl acetate phthalate, hydroxypropyl methylcellulose phthalate, methacrylic acid-methacrylic acid ester copolymers, cellulose acetate trimellitate, carboxymethyl ethyl cellulose, hydroxypropyl methyl cellulose acetate succinate, and the like. Examples of pharmaceutically acceptable antioxidants include: water-soluble antioxidants, such as ascorbic acid, cysteine hydrochloride, sodium bisulfate, sodium metabisulfate sodium sulfite and the like; oil-soluble antioxidants, such as ascorbyl palmitate, butylated hydroxyanisole, butylated hydroxytoluene, lecithin, propyl gallate, alpha-tocopherol, and the like; and metal-chelating agents, such as citric acid, ethylenediamine tetraacetic acid, sorbitol, tartaric acid, phosphoric acid, and the like.

Compositions may also be formulated to provide slow or controlled release of the active agent using, by way of example, hydroxypropyl methyl cellulose in varying proportions or other polymer matrices, liposomes and/or microspheres. In addition, the pharmaceutical compositions of the invention may contain opacifying agents and may be formulated so that they release the active agent only, or preferentially, in a certain portion of the gastrointestinal tract, optionally, in a delayed manner. Examples of embedding compositions which can be used include polymeric substances and waxes. The active agent can also be in micro-encapsulated form, optionally with one or more of the above-described excipients.

Suitable liquid dosage forms for oral administration include, by way of illustration, pharmaceutically acceptable emulsions, microemulsions, solutions, suspensions, syrups and elixirs. Liquid dosage forms typically comprise the active agent and an inert diluent, such as, for example, water or other solvents, solubilizing agents and emulsifiers, such as ethyl alcohol, isopropyl alcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl benzoate, propylene glycol, 1,3-butylene glycol, oils (for example, cottonseed, groundnut, corn, germ, olive, castor and sesame oils), glycerol, tetrahydrofuryl alcohol, polyethylene glycols and fatty acid esters of sorbitan, and mixtures thereof. Suspensions may contain suspending agents such as, for example, ethoxylated isostearyl alcohols, polyoxyethylene sorbitol and sorbitan esters, microcrystalline cellulose, aluminium metahydroxide, bentonite, agar-agar and tragacanth, and mixtures thereof.

When intended for oral administration, the pharmaceutical compositions of the invention may be packaged in a unit dosage form. The term “unit dosage form” refers to a physically discrete unit suitable for dosing a patient, that is, each unit containing a predetermined quantity of the active agent calculated to produce the desired therapeutic effect either alone or in combination with one or more additional units. For example, such unit dosage forms may be capsules, tablets, pills, and the like.

In another embodiment, the compositions of the invention are suitable for inhaled administration, and will typically be in the form of an aerosol or a powder. Such compositions are generally administered using well-known delivery devices, such as a nebulizer, dry powder, or metered-dose inhaler. Nebulizer devices produce a stream of high velocity air that causes the composition to spray as a mist that is carried into a patient's respiratory tract. An exemplary nebulizer formulation comprises the active agent dissolved in a carrier to form a solution, or micronized and combined with a carrier to form a suspension of micronized particles of respirable size. Dry powder inhalers administer the active agent as a free-flowing powder that is dispersed in a patient's air-stream during inspiration. An exemplary dry powder formulation comprises the active agent dry-blended with an excipient such as lactose, starch, mannitol, dextrose, polylactic acid, polylactide-co-glycolide, and combinations thereof. Metered-dose inhalers discharge a measured amount of the active agent using compressed propellant gas. An exemplary metered-dose formulation comprises a solution or suspension of the active agent in a liquefied propellant, such as a chlorofluorocarbon or hydrofluoroalkane. Optional components of such formulations include co-solvents, such as ethanol or pentane, and surfactants, such as sorbitan trioleate, oleic acid, lecithin, glycerin, and sodium lauryl sulfate. Such compositions are typically prepared by adding chilled or pressurized hydrofluoroalkane to a suitable container containing the active agent, ethanol (if present) and the surfactant (if present). To prepare a suspension, the active agent is micronized and then combined with the propellant. Alternatively, a suspension formulation can be prepared by spray drying a coating of surfactant on micronized particles of the active agent. The formulation is then loaded into an aerosol canister, which forms a portion of the inhaler.

Compounds of the invention can also be administered parenterally (for example, by subcutaneous, intravenous, intramuscular, or intraperitoneal injection). For such administration, the active agent is provided in a sterile solution, suspension, or emulsion. Exemplary solvents for preparing such formulations include water, saline, low molecular weight alcohols such as propylene glycol, polyethylene glycol, oils, gelatin, fatty acid esters such as ethyl oleate, and the like. Parenteral formulations may also contain one or more anti-oxidants, solubilizers, stabilizers, preservatives, wetting agents, emulsifiers, and dispersing agents. Surfactants, additional stabilizing agents or pH-adjusting agents (acids, bases or buffers) and anti-oxidants are particularly useful to provide stability to the formulation, for example, to minimize or avoid hydrolysis of ester and amide linkages that may be present in the compound. These formulations may be rendered sterile by use of a sterile injectable medium, a sterilizing agent, filtration, irradiation, or heat. In one particular embodiment, the parenteral formulation comprises an aqueous cyclodextrin solution as the pharmaceutically acceptable carrier. Suitable cyclodextrins include cyclic molecules containing six or more α-D-glucopyranose units linked at the 1,4 positions by a linkages as in amylase, β-cyclodextrin or cycloheptaamylose. Exemplary cyclodextrins include cyclodextrin derivatives such as hydroxypropyl and sulfobutyl ether cyclodextrins such as hydroxypropyl-p-cyclodextrin and sulfobutyl ether β-cyclodextrin. Exemplary buffers for such formulations include carboxylic acid-based buffers such as citrate, lactate and maleate buffer solutions.

Compounds of the invention can also be administered transdermally using known transdermal delivery systems and excipients. For example, the compound can be admixed with permeation enhancers, such as propylene glycol, polyethylene glycol monolaurate, azacycloalkan-2-ones and the like, and incorporated into a patch or similar delivery system. Additional excipients including gelling agents, emulsifiers and buffers, may be used in such transdermal compositions if desired.

Secondary Agents

The compounds of the invention may be useful as the sole treatment of a disease or may be combined with one or more additional therapeutic agents in order to obtain the desired therapeutic effect. Thus, in one embodiment, pharmaceutical compositions of the invention contain other drugs that are co-administered with a compound of the invention. For example, the composition may further comprise one or more drugs (also referred to as “secondary agents(s)”). Such therapeutic agents are well known in the art, and include adenosine receptor antagonists, α-adrenergic receptor antagonists, β₁-adrenergic receptor antagonists, β₂-adrenergic receptor agonists, dual-acting β-adrenergic receptor antagonist/α₁-receptor antagonists, advanced glycation end product breakers, aldosterone antagonists, aldosterone synthase inhibitors, aminopeptidase N inhibitors, androgens, angiotensin-converting enzyme inhibitors and dual-acting angiotensin-converting enzyme/neprilysin inhibitors, angiotensin-converting enzyme 2 activators and stimulators, angiotensin-II vaccines, anticoagulants, anti-diabetic agents, antidiarrheal agents, anti-glaucoma agents, anti-lipid agents, antinociceptive agents, anti-thrombotic agents, AT₁ receptor antagonists and dual-acting AT₁ receptor antagonist/neprilysin inhibitors and multifunctional angiotensin receptor blockers, bradykinin receptor antagonists, calcium channel blockers, chymase inhibitors, digoxin, diuretics, dopamine agonists, endothelin converting enzyme inhibitors, endothelin receptor antagonists, HMG-CoA reductase inhibitors, estrogens, estrogen receptor agonists and/or antagonists, monoamine reuptake inhibitors, muscle relaxants, natriuretic peptides and their analogs, natriuretic peptide clearance receptor antagonists, neprilysin inhibitors, nitric oxide donors, non-steroidal anti-inflammatory agents, N-methyl d-aspartate receptor antagonists, opioid receptor agonists, phosphodiesterase inhibitors, prostaglandin analogs, prostaglandin receptor agonists, renin inhibitors, selective serotonin reuptake inhibitors, sodium channel blocker, soluble guanylate cyclase stimulators and activators, tricyclic antidepressants, vasopressin receptor antagonists, and combinations thereof. Specific examples of these agents are detailed herein.

Accordingly, in yet another aspect of the invention, a pharmaceutical composition comprises a compound of the invention, a second active agent, and a pharmaceutically acceptable carrier. Third, fourth etc. active agents may also be included in the composition. In combination therapy, the amount of compound of the invention that is administered, as well as the amount of secondary agents, may be less than the amount typically administered in monotherapy.

Compounds of the invention may be physically mixed with the second active agent to form a composition containing both agents; or each agent may be present in separate and distinct compositions which are administered to the patient simultaneously or at separate times. For example, a compound of the invention can be combined with a second active agent using conventional procedures and equipment to form a combination of active agents comprising a compound of the invention and a second active agent. Additionally, the active agents may be combined with a pharmaceutically acceptable carrier to form a pharmaceutical composition comprising a compound of the invention, a second active agent and a pharmaceutically acceptable carrier. In this embodiment, the components of the composition are typically mixed or blended to create a physical mixture. The physical mixture is then administered in a therapeutically effective amount using any of the routes described herein.

Alternatively, the active agents may remain separate and distinct before administration to the patient. In this embodiment, the agents are not physically mixed together before administration but are administered simultaneously or at separate times as separate compositions. Such compositions can be packaged separately or may be packaged together in a kit. When administered at separate times, the secondary agent will typically be administered less than 24 hours after administration of the compound of the invention, ranging anywhere from concurrent with administration of the compound of the invention to about 24 hours post-dose. This is also referred to as sequential administration. Thus, a compound of the invention can be orally administered simultaneously or sequentially with another active agent using two tablets, with one tablet for each active agent, where sequential may mean being administered immediately after administration of the compound of the invention or at some predetermined time later (for example, one hour later or three hours later). It is also contemplated that the secondary agent may be administered more than 24 hours after administration of the compound of the invention. Alternatively, the combination may be administered by different routes of administration, that is, one orally and the other by inhalation.

In one embodiment, the kit comprises a first dosage form comprising a compound of the invention and at least one additional dosage form comprising one or more of the secondary agents set forth herein, in quantities sufficient to carry out the methods of the invention. The first dosage form and the second (or third, etc.) dosage form together comprise a therapeutically effective amount of active agents for the treatment or prevention of a disease or medical condition in a patient.

Secondary agent(s), when included, are present in a therapeutically effective amount such that they are typically administered in an amount that produces a therapeutically beneficial effect when co-administered with a compound of the invention. The secondary agent can be in the form of a pharmaceutically acceptable salt, solvate, optically pure stereoisomer, and so forth. The secondary agent may also be in the form of a prodrug, for example, a compound having a carboxylic acid group that has been esterified. Thus, secondary agents listed herein are intended to include all such forms, and are commercially available or can be prepared using conventional procedures and reagents.

In one embodiment, compounds of the invention are administered in combination with an adenosine receptor antagonist, representative examples of which include, but are not limited to, naxifylline, rolofylline, SLV-320, theophylline, and tonapofylline.

In one embodiment, compounds of the invention are administered in combination with an α-adrenergic receptor antagonist, representative examples of which include, but are not limited to, doxazosin, prazosin, tamsulosin, and terazosin.

Compounds of the invention may also be administered in combination with a β₁-adrenergic receptor antagonist (“β₁-blockers”). Representative β₁-blockers include, but are not limited to, acebutolol, alprenolol, amosulalol, arotinolol, atenolol, befunolol, betaxolol, bevantolol, bisoprolol, bopindolol, bucindolol, bucumolol, bufetolol, bufuralol, bunitrolol, bupranolol, bubridine, butofilolol, carazolol, carteolol, carvedilol, celiprolol, cetamolol, cloranolol, dilevalol, epanolol, esmolol, indenolol, labetolol, levobunolol, mepindolol, metipranolol, metoprolol such as metoprolol succinate and metoprolol tartrate, moprolol, nadolol, nadoxolol, nebivalol, nipradilol, oxprenolol, penbutolol, perbutolol, pindolol, practolol, pronethalol, propranolol, sotalol, sufinalol, talindol, tertatolol, tilisolol, timolol, toliprolol, xibenolol, and combinations thereof. In one particular embodiment, the β₁-antagonist is selected from atenolol, bisoprolol, metoprolol, propranolol, sotalol, and combinations thereof. Typically, the β₁-blocker will be administered in an amount sufficient to provide from about 2-900 mg per dose.

In one embodiment, compounds of the invention are administered in combination with a β₂-adrenergic receptor agonist, representative examples of which include, but are not limited to, albuterol, bitolterol, fenoterol, formoterol, indacaterol, isoetharine, levalbuterol, metaproterenol, pirbuterol, salbutamol, salmefamol, salmeterol, terbutaline, vilanterol, and the like Typically, the β₂-adrenergic receptor agonist will be administered in an amount sufficient to provide from about 0.05-500 μg per dose.

In one embodiment, compounds of the invention are administered in combination with an advanced glycation end product (AGE) breaker, examples of which include, by way of illustration and not limitation, alagebrium (or ALT-711), and TRC4149.

In another embodiment, compounds of the invention are administered in combination with an aldosterone antagonist, representative examples of which include, but are not limited to, eplerenone, spironolactone, and combinations thereof. Typically, the aldosterone antagonist will be administered in an amount sufficient to provide from about 5-300 mg per day.

In one embodiment, compounds of the invention are administered in combination with an aminopeptidase N or dipeptidyl peptidase III inhibitor, examples of which include, by way of illustration and not limitation, bestatin and PC 18 (2-amino-4-methylsulfonyl butane thiol, methionine thiol).

Compounds of the invention can also be administered in combination with an angiotensin-converting enzyme (ACE) inhibitor. Representative ACE inhibitors include, but are not limited to, accupril, alacepril, benazepril, benazeprilat, captopril, ceranapril, cilazapril, delapril, enalapril, enalaprilat, fosinopril, fosinoprilat, imidapril, lisinopril, moexipril, monopril, moveltopril, pentopril, perindopril, quinapril, quinaprilat, ramipril, ramiprilat, saralasin acetate, spirapril, temocapril, trandolapril, zofenopril, and combinations thereof. In a particular embodiment, the ACE inhibitor is selected from: benazepril, captopril, enalapril, lisinopril, ramipril, and combinations thereof. Typically, the ACE inhibitor will be administered in an amount sufficient to provide from about 1-150 mg per day.

In another embodiment, compounds of the invention are administered in combination with a dual-acting angiotensin-converting enzyme/neprilysin (ACE/NEP) inhibitor, examples of which include, but are not limited to: AVE-0848 ((4S,7S,12bR)-7-[3-methyl-2 (S)-sulfanylbutyramido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]-benzazepine-4-carboxylic acid); AVE-7688 (ilepatril) and its parent compound; BMS-182657 (2-[2-oxo-3 (S)-[3-phenyl-2(S)-sulfanylpropionamido]-2,3,4,5-tetrahydro-1H-1-benzazepin-1-yl]acetic acid); CGS-35601 (N-[1-[4-methyl-2(S)-sulfanylpentanamido]cyclopentylcarbonyl]-L-tryptophan); fasidotril; fasidotrilate; enalaprilat; ER-32935 ((3R,6S,9aR)-6-[3(S)-methyl-2(S)-sulfanylpentanamido]-5-oxoperhydrothiazolo[3,2-a]azepine-3-carboxylic acid); gempatrilat; MDL-101264 ((4S,7S,12bR)-7-[2(S)-(2-morpholinoacetylthio)-3-phenylpropionamido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]benzazepine-4-carboxylic acid); MDL-101287 ([4S-[4α,7α(R*), 12bβ]]-7-[2-(carboxymethyl)-3-phenylpropionamido]-6-oxo-1,2,3,4,6,7,8,12b-octahydropyrido[2,1-a][2]benzazepine-4-carboxylic acid); omapatrilat; RB-105 (N-[2(S)-(mercaptomethyl)-3(R)-phenylbutyl]-L-alanine); sampatrilat; SA-898 ((2R,4R)—N-[2-(2-hydroxyphenyl)-3-(3-mercaptopropionyl)thiazolidin-4-ylcarbonyl]-L-phenylalanine); Sch-50690 (N-[1(S)-carboxy-2-[N2-(methanesulfonyl)-L-lysylamino]ethyl]-L-valyl-L-tyrosine); and combinations thereof, may also be included. In one particular embodiment, the ACE/NEP inhibitor is selected from: AVE-7688, enalaprilat, fasidotril, fasidotrilate, omapatrilat, sampatrilat, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an angiotensin-converting enzyme 2 (ACE2) activator or stimulator.

In one embodiment, compounds of the invention are administered in combination with an angiotensin-II vaccine, examples of which include, but are not limited to ATR12181 and CYT006-AngQb.

In one embodiment, compounds of the invention are administered in combination with an anticoagulant, representative examples of which include, but are not limited to: coumarins such as warfarin; heparin; and direct thrombin inhibitors such as argatroban, bivalirudin, dabigatran, and lepirudin.

In yet another embodiment, compounds of the invention are administered in combination with an anti-diabetic agent. Representative anti-diabetic agents include injectable drugs as well as orally effective drugs, and combinations thereof. Examples of injectable drugs include, but are not limited to, insulin and insulin derivatives. Examples of orally effective drugs include, but are not limited to: biguanides such as metformin; glucagon antagonists; α-glucosidase inhibitors such as acarbose and miglitol; dipeptidyl peptidase IV inhibitors (DPP-IV inhibitors) such as alogliptin, denagliptin, linagliptin, saxagliptin, sitagliptin, and vildagliptin; meglitinides such as repaglinide; oxadiazolidinediones; sulfonylureas such as chlorpropamide, glimepiride, glipizide, glyburide, and tolazamide; thiazolidinediones such as pioglitazone and rosiglitazone; and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with antidiarrheal treatments. Representative treatment options include, but are not limited to, oral rehydration solutions (ORS), loperamide, diphenoxylate, and bismuth sabsalicylate.

In yet another embodiment, a compound of the invention is administered in combination with an anti-glaucoma agent. Representative anti-glaucoma agents include, but are not limited to: α-adrenergic agonists such as brimonidine; β₁-adrenergic receptor antagonists; topical β₁-blockers such as betaxolol, levobunolol, and timolol; carbonic anhydrase inhibitors such as acetazolamide, brinzolamide, or dorzolamide; cholinergic agonists such as cevimeline and DMXB-anabaseine; epinephrine compounds; miotics such as pilocarpine; and prostaglandin analogs.

In yet another embodiment, compounds of the invention are administered in combination with an anti-lipid agent. Representative anti-lipid agents include, but are not limited to: cholesteryl ester transfer protein inhibitors (CETPs) such as anacetrapib, dalcetrapib, and torcetrapib; statins such as atorvastatin, fluvastatin, lovastatin, pravastatin, rosuvastatin and simvastatin; and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an anti-thrombotic agent. Representative anti-thrombotic agents include, but are not limited to: aspirin; anti-platelet agents such as clopidogrel, prasugrel, and ticlopidine; heparin, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an AT₁ receptor antagonist, also known as angiotensin II type 1 receptor blockers (ARBs). Representative ARBs include, but are not limited to, abitesartan, azilsartan (e.g., azilsartan medoxomil), benzyllosartan, candesartan, candesartan cilexetil, elisartan, embusartan, enoltasosartan, eprosartan, EXP3174, fonsartan, forasartan, glycyllosartan, irbesartan, isoteoline, losartan, medoximil, milfasartan, olmesartan (e.g., olmesartan medoxomil), opomisartan, pratosartan, ripisartan, saprisartan, saralasin, sarmesin, TAK-591, tasosartan, telmisartan, valsartan, zolasartan, and combinations thereof. In a particular embodiment, the ARB is selected from azilsartan medoxomil, candesartan cilexetil, eprosartan, irbesartan, losartan, olmesartan medoxomil, irbesartan, saprisartan, tasosartan, telmisartan, valsartan, and combinations thereof. Exemplary salts and/or prodrugs include candesartan cilexetil, eprosartan mesylate, losartan potassium salt, and olmesartan medoxomil. Typically, the ARB will be administered in an amount sufficient to provide from about 4-600 mg per dose, with exemplary daily dosages ranging from 20-320 mg per day.

Compounds of the invention may also be administered in combination with a dual-acting agent, such as an AT₁ receptor antagonist/neprilysin inhibitor (ARB/NEP) inhibitor, examples of which include, but are not limited to, compounds described in U.S. Publication Nos. 2008/0269305 and 2009/0023228, both to Allegretti et al. filed on Apr. 23, 2008, such as the compound, 4′-{2-ethoxy-4-ethyl-5-[((S)-2-mercapto-4-methylpentanoylamino)-methyl]imidazol-1-ylmethyl}-3′-fluorobiphenyl-2-carboxylic acid.

Compounds of the invention may also be administered in combination with multifunctional angiotensin receptor blockers as described in Kurtz & Klein (2009) Hypertension Research 32:826-834.

In one embodiment, compounds of the invention are administered in combination with a bradykinin receptor antagonist, for example, icatibant (HOE-140). It is expected that this combination therapy may present the advantage of preventing angioedema or other unwanted consequences of elevated bradykinin levels.

In one embodiment, compounds of the invention are administered in combination with a calcium channel blocker. Representative calcium channel blockers include, but are not limited to, amlodipine, anipamil, aranipine, barnidipine, bencyclane, benidipine, bepridil, clentiazem, cilnidipine, cinnarizine, diltiazem, efonidipine, elgodipine, etafenone, felodipine, fendiline, flunarizine, gallopamil, isradipine, lacidipine, lercanidipine, lidoflazine, lomerizine, manidipine, mibefradil, nicardipine, nifedipine, niguldipine, niludipine, nilvadipine, nimodipine, nisoldipine, nitrendipine, nivaldipine, perhexiline, prenylamine, ryosidine, semotiadil, terodiline, tiapamil, verapamil, and combinations thereof. In a particular embodiment, the calcium channel blocker is selected from amlodipine, bepridil, diltiazem, felodipine, isradipine, lacidipine, nicardipine, nifedipine, niguldipine, niludipine, nimodipine, nisoldipine, ryosidine, verapamil, and combinations thereof. Typically, the calcium channel blocker will be administered in an amount sufficient to provide from about 2-500 mg per dose.

In one embodiment, compounds of the invention are administered in combination with a chymase inhibitor, such as TPC-806 and 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[{3,4-dioxo-1-phenyl-7-(2-pyridyloxy)}-2-heptyl]acetamide (NK3201).

In one embodiment, compounds of the invention are administered in combination with a diuretic. Representative diuretics include, but are not limited to: carbonic anhydrase inhibitors such as acetazolamide and dichlorphenamide; loop diuretics, which include sulfonamide derivatives such as acetazolamide, ambuside, azosernide, bumetanide, butazolamide, chloraminophenamide, clofenamide, clopamide, clorexolone, disulfamide, ethoxolamide, furosemide, mefruside, methazolamide, piretanide, torsemide, tripamide, and xipamide, as well as non-sulfonamide diuretics such as ethacrynic acid and other phenoxyacetic acid compounds such as tienilic acid, indacrinone and quincarbate; osmotic diuretics such as mannitol; potassium-sparing diuretics, which include aldosterone antagonists such as spironolactone, and Na⁺ channel inhibitors such as amiloride and triamterene; thiazide and thiazide-like diuretics such as althiazide, bendroflumethiazide, benzylhydrochlorothiazide, benzthiazide, buthiazide, chlorthalidone, chlorothiazide, cyclopenthiazide, cyclothiazide, epithiazide, ethiazide, fenquizone, flumethiazide, hydrochlorothiazide, hydroflumethiazide, indapamide, methylclothiazide, meticrane, metolazone, paraflutizide, polythiazide, quinethazone, teclothiazide, and trichloromethiazide; and combinations thereof. In a particular embodiment, the diuretic is selected from amiloride, bumetanide, chlorothiazide, chlorthalidone, dichlorphenamide, ethacrynic acid, furosemide, hydrochlorothiazide, hydroflumethiazide, indapamide, methylclothiazide, metolazone, torsemide, triamterene, and combinations thereof. The diuretic will be administered in an amount sufficient to provide from about 5-50 mg per day, more typically 6-25 mg per day, with common dosages being 6.25 mg, 12.5 mg or 25 mg per day.

Compounds of the invention may also be administered in combination with an endothelin converting enzyme (ECE) inhibitor, examples of which include, but are not limited to, phosphoramidon, CGS 26303, and combinations thereof.

In a particular embodiment, compounds of the invention are administered in combination with an endothelin receptor antagonist. Representative endothelin receptor antagonists include, but are not limited to: selective endothelin receptor antagonists that affect endothelin A receptors, such as avosentan, ambrisentan, atrasentan, BQ-123, clazosentan, darusentan, sitaxentan, and zibotentan; and dual endothelin receptor antagonists that affect both endothelin A and B receptors, such as bosentan, macitentan, tezosentan).

In yet another embodiment, a compound of the invention is administered in combination with one or more HMG-CoA reductase inhibitors, which are also known as statins. Representative statins include, but are not limited to, atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin.

In one embodiment, compounds of the invention are administered in combination with a monoamine reuptake inhibitor, examples of which include, by way of illustration and not limitation, norepinephrine reuptake inhibitors such as atomoxetine, buproprion and the buproprion metabolite hydroxybuproprion, maprotiline, reboxetine, and viloxazine; selective serotonin reuptake inhibitors (SSRIs) such as citalopram and the citalopram metabolite desmethylcitalopram, dapoxetine, escitalopram (e.g., escitalopram oxalate), fluoxetine and the fluoxetine desmethyl metabolite norfluoxetine, fluvoxamine (e.g., fluvoxamine maleate), paroxetine, sertraline and the sertraline metabolite demethylsertraline; dual serotonin-norepinephrine reuptake inhibitors (SNRIs) such as bicifadine, duloxetine, milnacipran, nefazodone, and venlafaxine; and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with a muscle relaxant, examples of which include, but are not limited to: carisoprodol, chlorzoxazone, cyclobenzaprine, diflunisal, metaxalone, methocarbamol, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a natriuretic peptide or analog, examples of which include but are not limited to: carperitide, CD-NP (Nile Therapeutics), CU-NP, nesiritide, PL-3994 (Palatin Technologies, Inc.), ularitide, cenderitide, and compounds described in Ogawa et al (2004) J. Biol. Chem. 279:28625-31. These compounds are also referred to as natriuretic peptide receptor-A (NPR-A) agonists. In another embodiment, compounds of the invention are administered in combination with a natriuretic peptide clearance receptor (NPR-C) antagonist such as SC-46542, cANF (4-23), and AP-811 (Veale (2000) Bioorg Med Chem Lett 10:1949-52). For example, AP-811 has shown synergy when combined with the NEP inhibitor, thiorphan (Wegner (1995) Clin. Exper. Hypert. 17:861-876).

In another embodiment, compounds of the invention are administered in combination with a neprilysin (NEP) inhibitor. Representative NEP inhibitors include, but are not limited to: AHU-377; candoxatril; candoxatrilat; dexecadotril ((+)-N-[2(R)-(acetylthiomethyl)-3-phenylpropionyl]glycine benzyl ester); CGS-24128 (3-[3-(biphenyl-4-yl)-2-(phosphonomethylamino)propionamido]propionic acid); CGS-24592 ((S)-3-[3-(biphenyl-4-yl)-2-(phosphonomethylamino)propionamido]propionic acid); CGS-25155 (N-[9(R)-(acetylthiomethyl)-10-oxo-1-azacyclodecan-2(S)-ylcarbonyl]-4(R)-hydroxy-L-proline benzyl ester); 3-(1-carbamoylcyclohexyl)propionic acid derivatives described in WO 2006/027680 to Hepworth et al. (Pfizer Inc.); JMV-390-1 (2(R)-benzyl-3-(N-hydroxycarbamoyl)propionyl-L-isoleucyl-L-leucine); ecadotril; phosphoramidon; retrothiorphan; RU-42827 (2-(mercaptomethyl)-N-(4-pyridinyl)benzenepropionamide); RU-44004 (N-(4-morpholinyl)-3-phenyl-2-(sulfanylmethyl)propionamide); SCH-32615 ((S)—N—[N-(1-carboxy-2-phenylethyl)-L-phenylalanyl]-β-alanine) and its prodrug SCH-34826 ((S)—N—[N-[1-[[(2,2-dimethyl-1,3-dioxolan-4-yl)methoxy]carbonyl]-2-phenylethyl]-L-phenylalanyl]-3-alanine); sialorphin; SCH-42495 (N-[2(S)-(acetylsulfanylmethyl)-3-(2-methylphenyl)propionyl]-L-methionine ethyl ester); spinorphin; SQ-28132 (N-[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]leucine); SQ-28603 (N-[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]-β-alanine); SQ-29072 (7-[[2-(mercaptomethyl)-1-oxo-3-phenylpropyl]amino]heptanoic acid); thiorphan and its prodrug racecadotril; UK-69578 (cis-4-[[[1-[2-carboxy-3-(2-methoxyethoxy)propyl]cyclopentyl]carbonyl]amino]cyclohexanecarboxylic acid); UK-447,841 (2-{1-[3-(4-chlorophenyl)propylcarbamoyl]-cyclopentylmethyl}-4-methoxybutyric acid); UK-505,749 ((R)-2-methyl-3-{1-[3-(2-methylbenzothiazol-6-yl)propylcarbamoyl]cyclopentyl}propionic acid); 5-biphenyl-4-yl-4-(3-carboxypropionylamino)-2-methylpentanoic acid and 5-biphenyl-4-yl-4-(3-carboxypropionylamino)-2-methylpentanoic acid ethyl ester (WO 2007/056546); daglutril [(3S,2′R)-3-{1-[2′-(ethoxycarbonyl)-4′-phenylbutyl]-cyclopentan-1-carbonylamino}-2,3,4,5-tetrahydro-2-oxo-1H-1-benzazepine-1-acetic acid] described in WO 2007/106708 to Khder et al. (Novartis AG); and combinations thereof. In a particular embodiment, the NEP inhibitor is selected from AHU-377, candoxatril, candoxatrilat, CGS-24128, phosphoramidon, SCH-32615, SCH-34826, SQ-28603, thiorphan, and combinations thereof. In a particular embodiment, the NEP inhibitor is a compound such as daglutril or CGS-26303 ([N-[2-(biphenyl-4-yl)-1(S)-(1H-tetrazol-5-yl)ethyl]amino]methylphosphonic acid), which have activity both as inhibitors of the endothelin converting enzyme (ECE) and of NEP. Other dual acting ECE/NEP compounds can also be used. The NEP inhibitor will be administered in an amount sufficient to provide from about 20-800 mg per day, with typical daily dosages ranging from 50-700 mg per day, more commonly 100-600 or 100-300 mg per day.

In one embodiment, compounds of the invention are administered in combination with a nitric oxide donor, examples of which include, but are not limited to nicorandil; organic nitrates such as pentaerythritol tetranitrate; and sydnonimines such as linsidomine and molsidomine.

In yet another embodiment, compounds of the invention are administered in combination with a non-steroidal anti-inflammatory agent (NSAID). Representative NSAIDs include, but are not limited to: acemetacin, acetyl salicylic acid, alclofenac, alminoprofen, amfenac, amiprilose, amoxiprin, anirolac, apazone, azapropazone, benorilate, benoxaprofen, bezpiperylon, broperamole, bucloxic acid, carprofen, clidanac, diclofenac, diflunisal, diftalone, enolicam, etodolac, etoricoxib, fenbufen, fenclofenac, fenclozic acid, fenoprofen, fentiazac, feprazone, flufenamic acid, flufenisal, fluprofen, flurbiprofen, furofenac, ibufenac, ibuprofen, indomethacin, indoprofen, isoxepac, isoxicam, ketoprofen, ketorolac, lofemizole, lornoxicam, meclofenamate, meclofenamic acid, mefenamic acid, meloxicam, mesalamine, miroprofen, mofebutazone, nabumetone, naproxen, niflumic acid, oxaprozin, oxpinac, oxyphenbutazone, phenylbutazone, piroxicam, pirprofen, pranoprofen, salsalate, sudoxicam, sulfasalazine, sulindac, suprofen, tenoxicam, tiopinac, tiaprofenic acid, tioxaprofen, tolfenamic acid, tolmetin, triflumidate, zidometacin, zomepirac, and combinations thereof. In a particular embodiment, the NSAID is selected from etodolac, flurbiprofen, ibuprofen, indomethacin, ketoprofen, ketorolac, meloxicam, naproxen, oxaprozin, piroxicam, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with an N-methyl d-aspartate (NMDA) receptor antagonist, examples of which include, by way of illustration and not limitation, including amantadine, dextromethorphan, dextropropoxyphene, ketamine, ketobemidone, memantine, methadone, and so forth.

In still another embodiment, compounds of the invention are administered in combination with an opioid receptor agonist (also referred to as opioid analgesics). Representative opioid receptor agonists include, but are not limited to: buprenorphine, butorphanol, codeine, dihydrocodeine, fentanyl, hydrocodone, hydromorphone, levallorphan, levorphanol, meperidine, methadone, morphine, nalbuphine, nalmefene, nalorphine, naloxone, naltrexone, nalorphine, oxycodone, oxymorphone, pentazocine, propoxyphene, tramadol, and combinations thereof. In certain embodiments, the opioid receptor agonist is selected from codeine, dihydrocodeine, hydrocodone, hydromorphone, morphine, oxycodone, oxymorphone, tramadol, and combinations thereof.

In a particular embodiment, compounds of the invention are administered in combination with a phosphodiesterase (PDE) inhibitor, particularly a PDE-V inhibitor. Representative PDE-V inhibitors include, but are not limited to, avanafil, lodenafil, mirodenafil, sildenafil (Revatio®), tadalafil (Adcirca®), vardenafil (Levitra®), and udenafil.

In another embodiment, compounds of the invention are administered in combination with a prostaglandin analog (also referred to as prostanoids or prostacyclin analogs). Representative prostaglandin analogs include, but are not limited to, beraprost sodium, bimatoprost, epoprostenol, iloprost, latanoprost, tafluprost, travoprost, and treprostinil, with bimatoprost, latanoprost, and tafluprost being of particular interest. In yet another embodiment, compounds of the invention are administered in combination with a prostaglandin receptor agonist, examples of which include, but are not limited to, bimatoprost, latanoprost, travoprost, and so forth.

Compounds of the invention may also be administered in combination with a renin inhibitor, examples of which include, but are not limited to, aliskiren, enalkiren, remikiren, and combinations thereof.

In another embodiment, compounds of the invention are administered in combination with a selective serotonin reuptake inhibitor (SSRI). Representative SSRIs include, but are not limited to: citalopram and the citalopram metabolite desmethylcitalopram, dapoxetine, escitalopram (e.g., escitalopram oxalate), fluoxetine and the fluoxetine desmethyl metabolite norfluoxetine, fluvoxamine (e.g., fluvoxamine maleate), paroxetine, sertraline and the sertraline metabolite demethylsertraline, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a 5-HT_(1D) serotonin receptor agonist, examples of which include, by way of illustration and not limitation, triptans such as almotriptan, avitriptan, eletriptan, frovatriptan, naratriptan rizatriptan, sumatriptan, and zolmitriptan.

In one embodiment, compounds of the invention are administered in combination with a sodium channel blocker, examples of which include, by way of illustration and not limitation, carbamazepine, fosphenytoin, lamotrignine, lidocaine, mexiletine, oxcarbazepine, phenytoin, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a soluble guanylate cyclase stimulator or activator, examples of which include, but are not limited to ataciguat, riociguat, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a tricyclic antidepressant (TCA), examples of which include, by way of illustration and not limitation, amitriptyline, amitriptylinoxide, butriptyline, clomipramine, demexiptiline, desipramine, dibenzepin, dimetacrine, dosulepin, doxepin, imipramine, imipraminoxide, lofepramine, melitracen, metapramine, nitroxazepine, nortriptyline, noxiptiline, pipofezine, propizepine, protriptyline, quinupramine, and combinations thereof.

In one embodiment, compounds of the invention are administered in combination with a vasopressin receptor antagonist, examples of which include, by way of illustration and not limitation, conivaptan and tolvaptan.

Combined secondary therapeutic agents may also be helpful in further combination therapy with compounds of the invention. For example, compounds of the invention can be combined with a diuretic and an ARB, or a calcium channel blocker and an ARB, or a diuretic and an ACE inhibitor, or a calcium channel blocker and a statin. Specific examples include, a combination of the ACE inhibitor enalapril (in the maleate salt form) and the diuretic hydrochlorothiazide, which is sold under the mark Vaseretic®, or a combination of the calcium channel blocker amlodipine (in the besylate salt form) and the ARB olmesartan (in the medoxomil prodrug form), or a combination of a calcium channel blocker and a statin, all may also be used with the compounds of the invention. Other therapeutic agents such as α₂-adrenergic receptor agonists and vasopressin receptor antagonists may also be helpful in combination therapy. Exemplary α₂-adrenergic receptor agonists include clonidine, dexmedetomidine, and guanfacine.

The following formulations illustrate representative pharmaceutical compositions of the invention.

Exemplary Hard Gelatin Capsules for Oral Administration

A compound of the invention (50 g), 440 g spray-dried lactose and 10 g magnesium stearate are thoroughly blended. The resulting composition is then loaded into hard gelatin capsules (500 mg of composition per capsule). Alternately, a compound of the invention (20 mg) is thoroughly blended with starch (89 mg), microcrystalline cellulose (89 mg) and magnesium stearate (2 mg). The mixture is then passed through a No. 45 mesh U.S. sieve and loaded into a hard gelatin capsule (200 mg of composition per capsule).

Alternately, a compound of the invention (30 g), a secondary agent (20 g), 440 g spray-dried lactose and 10 g magnesium stearate are thoroughly blended, and processed as described above.

Exemplary Gelatin Capsule Formulation for Oral Administration

A compound of the invention (100 mg) is thoroughly blended with polyoxyethylene sorbitan monooleate (50 mg) and starch powder (250 mg). The mixture is then loaded into a gelatin capsule (400 mg of composition per capsule). Alternately, a compound of the invention (70 mg) and a secondary agent (30 mg) are thoroughly blended with polyoxyethylene sorbitan monooleate (50 mg) and starch powder (250 mg), and the resulting mixture loaded into a gelatin capsule (400 mg of composition per capsule).

Alternately, a compound of the invention (40 mg) is thoroughly blended with microcrystalline cellulose (Avicel PH 103; 259.2 mg) and magnesium stearate (0.8 mg). The mixture is then loaded into a gelatin capsule (Size #1, White, Opaque) (300 mg of composition per capsule).

Exemplary Tablet Formulation for Oral Administration

A compound of the invention (10 mg), starch (45 mg) and microcrystalline cellulose (35 mg) are passed through a No. 20 mesh U.S. sieve and mixed thoroughly. The granules so produced are dried at 50-60° C. and passed through a No. 16 mesh U.S. sieve. A solution of polyvinylpyrrolidone (4 mg as a 10% solution in sterile water) is mixed with sodium carboxymethyl starch (4.5 mg), magnesium stearate (0.5 mg), and talc (1 mg), and this mixture is then passed through a No. 16 mesh U.S. sieve. The sodium carboxymethyl starch, magnesium stearate and talc are then added to the granules. After mixing, the mixture is compressed on a tablet machine to afford a tablet weighing 100 mg.

Alternately, a compound of the invention (250 mg) is thoroughly blended with microcrystalline cellulose (400 mg), silicon dioxide fumed (10 mg), and stearic acid (5 mg). The mixture is then compressed to form tablets (665 mg of composition per tablet).

Alternately, a compound of the invention (400 mg) is thoroughly blended with cornstarch (50 mg), croscarmellose sodium (25 mg), lactose (120 mg), and magnesium stearate (5 mg). The mixture is then compressed to form a single-scored tablet (600 mg of composition per tablet).

Alternately, a compound of the invention (100 mg) is thoroughly blended with cornstarch (100 mg) with an aqueous solution of gelatin (20 mg). The mixture is dried and ground to a fine powder. Microcrystalline cellulose (50 mg) and magnesium stearate (5 mg) are then admixed with the gelatin formulation, granulated and the resulting mixture compressed to form tablets (100 mg of the compound of the invention per tablet).

Exemplary Suspension Formulation for Oral Administration

The following ingredients are mixed to form a suspension containing 100 mg of the compound of the invention per 10 mL of suspension:

Ingredients Amount Compound of the invention 1.0 g Fumaric acid 0.5 g Sodium chloride 2.0 g Methyl paraben 0.15 g  Propyl paraben 0.05 g  Granulated sugar 25.5 g  Sorbitol (70% solution) 12.85 g  Veegum ® K (magnesium aluminum silicate) 1.0 g Flavoring 0.035 mL Colorings  0.5 mg Distilled water q.s. to 100 mL

Exemplary Liquid Formulation for Oral Administration

A suitable liquid formulation is one with a carboxylic acid-based buffer such as citrate, lactate and maleate buffer solutions. For example, a compound of the invention (which may be pre-mixed with DMSO) is blended with a 100 mM ammonium citrate buffer and the pH adjusted to pH 5, or is blended with a 100 mM citric acid solution and the pH adjusted to pH 2. Such solutions may also include a solubilizing excipient such as a cyclodextrin, for example the solution may include 10 wt % hydroxypropyl-β-cyclodextrin.

Other suitable formulations include a 5% NaHCO₃ solution, with or without cyclodextrin.

Exemplary Injectable Formulation for Administration by Injection

A compound of the invention (0.2 g) is blended with 0.4 M sodium acetate buffer solution (2.0 mL). The pH of the resulting solution is adjusted to pH 4 using 0.5 N aqueous hydrochloric acid or 0.5 N aqueous sodium hydroxide, as necessary, and then sufficient water for injection is added to provide a total volume of 20 mL. The mixture is then filtered through a sterile filter (0.22 micron) to provide a sterile solution suitable for administration by injection.

Exemplary Compositions for Administration by Inhalation

A compound of the invention (0.2 mg) is micronized and then blended with lactose (25 mg). This blended mixture is then loaded into a gelatin inhalation cartridge. The contents of the cartridge are administered using a dry powder inhaler, for example.

Alternately, a micronized compound of the invention (10 g) is dispersed in a solution prepared by dissolving lecithin (0.2 g) in demineralized water (200 mL). The resulting suspension is spray dried and then micronized to form a micronized composition comprising particles having a mean diameter less than about 1.5 μm. The micronized composition is then loaded into metered-dose inhaler cartridges containing pressurized 1,1,1,2-tetrafluoroethane in an amount sufficient to provide about 10 μg to about 500 μg of the compound of the invention per dose when administered by the inhaler.

Alternately, a compound of the invention (25 mg) is dissolved in citrate buffered (pH 5) isotonic saline (125 mL). The mixture is stirred and sonicated until the compound is dissolved. The pH of the solution is checked and adjusted, if necessary, to pH 5 by slowly adding aqueous 1 N NaOH. The solution is administered using a nebulizer device that provides about 10 μg to about 500 μg of the compound of the invention per dose.

EXAMPLES

The following Preparations and Examples are provided to illustrate specific embodiments of the invention. These specific embodiments, however, are not intended to limit the scope of the invention in any way unless specifically indicated.

The following abbreviations have the following meanings unless otherwise indicated and any other abbreviations used herein and not defined have their standard, generally accepted meaning:

-   -   AcOH acetic acid     -   BOC t-butoxycarbonyl (—C(O)OC(CH₃)₃)     -   (BOC)₂O di-t-butyl dicarbonate     -   Bn benzyl     -   DCC dicyclohexylcarbodiimide     -   DCM dichloromethane or methylene chloride     -   DIBAL diisobutylaluminum hydride     -   DIPEA N,N-diisopropylethylamine     -   DMAP 4-dimethylaminopyridine     -   DMF N,N-dimethylformamide     -   DMSO dimethyl sulfoxide     -   Dnp 2,4-dinitrophenyl     -   EDC 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide     -   Et₃N triethylamine     -   Et₂O diethyl ether     -   EtOAc ethyl acetate     -   EtOH ethanol     -   HEPES 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid     -   HOBt 1-hydroxybenzotriazole     -   LiHMDS lithium hexamethyl disilazide     -   Mca (7-methoxycoumarin-4-yl)acyl     -   MeCN acetonitrile     -   MeOH methanol     -   MTBE methyl t-butyl ether     -   NaHMDS sodium hexamethyldisilazide     -   Pd(dppf)₂Cl₂ 1,1-bis(diphenylphosphino) ferrocene palladium         chloride     -   Pd(PPh₃)₄ tetrakis(triphenylphosphine)palladium(0)     -   PE petroleum ether     -   SilicaCat® DPP-Pd silica based diphenylphosphine palladium (II)         catalyst     -   SilicaCat® Pd(0) silica based palladium (0) catalyst     -   TFA trifluoroacetic acid     -   THF tetrahydrofuran

Unless noted otherwise, all materials, such as reagents, starting materials and solvents, were purchased from commercial suppliers (such as Sigma-Aldrich, Fluka Riedel-de Haën, and the like) and were used without further purification.

Reactions were run under nitrogen atmosphere, unless noted otherwise. The progress of reactions were monitored by thin layer chromatography (TLC), analytical high performance liquid chromatography (anal. HPLC), and mass spectrometry, the details of which are given in specific examples. Solvents used in analytical HPLC were as follows: solvent A was 98% H₂O/2% MeCN/1.0 mL/L TFA; solvent B was 90% MeCN/10% H₂O/1.0 mL/L TFA.

Reactions were worked up as described specifically in each preparation for example; commonly reaction mixtures were purified by extraction and other purification methods such as temperature-, and solvent-dependent crystallization, and precipitation. In addition, reaction mixtures were routinely purified by preparative HPLC, typically using Microsorb C18 and Microsorb BDS column packings and conventional eluents. Progress of reactions was typically measured by liquid chromatography mass spectrometry (LCMS). Characterization of isomers were done by Nuclear Overhauser effect spectroscopy (NOE). Characterization of reaction products was routinely carried out by mass and ¹H-NMR spectrometry. For NMR measurement, samples were dissolved in deuterated solvent (CD₃OD, CDCl₃, or DMSO-d₆), and ¹H-NMR spectra were acquired with a Varian Gemini 2000 instrument (400 MHz) under standard observation conditions. Mass spectrometric identification of compounds was typically conducted using an electrospray ionization method (ESMS) with an Applied Biosystems (Foster City, Calif.) model API 150 EX instrument or an Agilent (Palo Alto, Calif.) model 1200 LC/MSD instrument.

Preparation 1 Acetoxy(diethoxyphosphorvl)acetic Acid Ethyl Ester

Ethyl 2-oxoacetate (50%) (74 g, 724.8 mmol) was added dropwise with stirring at 0° C. to a solution of diethyl hydrogen phosphite (50 g, 362.1 mmol) in toluene (100 mL), under nitrogen. Et₃N (110 g, 1.1 mol) was added dropwise with stirring at 0° C. The resulting solution was stirred for 1 hour at room temperature. To the mixture was added acetic anhydride (37 g, 362.4 mmol) dropwise with stirring at 0° C. The resulting solution was stirred overnight at room temperature. The pH value of the solution was adjusted to 6 with 2N HCl. The resulting solution was extracted with DCM (3×150 mL) and the organic layers were combined, dried over Na₂SO₄, and concentrated under vacuum. The residue was loaded onto a silica gel column with EtOAc:hexanes (1:2˜1:5) to yield the title compound (52 g) as a light yellow liquid.

Preparation 2 (R)-4-Amino-5-biphenyl-4-yl-2-hydroxypentanoic Acid Ethyl Ester

A solution of acetoxy(diethoxyphosphoryl)acetic acid ethyl ester (15.6 g, 55.3 mmol, 1.2 equiv) in THF (dried) (150 mL), under nitrogen, was cooled to −78° C. LiHMDS (1M in THF) (55.3 mL) was added dropwise with stirring at −78° C. After stirring for 30 minutes at that temperature, a solution of crude ((R)-2-biphenyl-4-yl-1-formylethyl)carbamic acid t-butyl ester (15.0 g, 1.0 eq.) in THF (dried) (30 mL) was added dropwise over 15 minutes. Stirring was continued for 1.5 hours at −78° C. before the mixture was poured into a cold solution with water (200 mL) and EtOAc (200 mL). The organic layer was repeatedly separated and the aqueous layer was re-extracted with EtOAc (2×100 mL). The combined organic layers were dried over Na₂SO₄, filtered, and evaporated, and the residue was purified by flash chromatography (EtOAc/hexanes=0˜1:10) to give Compound 1 (10.5 g) as a white solid.

A stirred solution of Compound 1 (10.5 g, 23.2 mmol) in EtOH (anhydrous) (100 mL) was combined with palladium carbon (1.0 g), under nitrogen. The mixture was purged four times with hydrogen and then hydrogen was bubbled over 2 hours at room temperature. The palladium carbon was filtered out, and the filtrate was concentrated under vacuum to yield crude Compound 2 (10.0 g) as a pale-yellow oil, which was used without further purification.

Compound 2 (10.0 g, 22.0 mmol) in EtOH (anhydrous) (100 mL) was combined with potassium carbonate (6.1 g, 44.1 mmol) and the resulting solution was stirred for 2 hours at room temperature. The solids were filtered out and the filtrate was concentrated under vacuum. The residue was loaded onto a silica gel column (EtOAc/hexanes=0˜1:5) to yield Compound 3 (6.0 g) as a white solid.

Compound 3 (6.0 g, 14.5 mmol) was dissolved in DCM (dried) (120 mL), and HCl was bubbled into the mixture over 5-6 hours at room temperature. Solid precipitate was observed. The mixture was concentrated to half volume then filtered. The solids were collected and washed with cold EtOAc, and dried over reduced pressure to yield the title compound (4.2 g) as an off-white solid HCl salt. LC-MS (ES, m/z): 314 [M−HCl+H]⁺.

¹H NMR (300 MHz, DMSO): δ (ppm)=8.07 (s, 1.9H), 7.96 (s, 1.2H), 7.65-7.69 (m, 4.0H), 7.45-7.50 (m, 2.0H), 7.33-7.39 (m, 3.0H), 6.05-6.07 (m, 0.63H), 5.88-5.90 (m, 0.88H), 4.32-4.38 (m, 0.80H), 4.18-4.31 (m, 0.51H), 4.05-4.11 (m, 2H), 3.50 (s, 1H), 2.75-3.05 (m, 2.8H), 1.83-1.94 (m, 1H), 1.71-1.82 (m, 1H), 1.10-1.20 (m, 3.3H).

Preparation 3 (S)-2-(4-Bromobenzyl)-5-oxopyrrolidine-1-carboxylic Acid t-Butyl Ester

To a solution of (R)-2-amino-3-(4-bromophenyl)propionic acid (50 g, 0.2 mol) in MeCN (700 mL) was added a solution of NaOH (16.4 g, 0.4 mol) in water (700 mL) at −5° C. After stirring for 10 minutes, a solution of (BOC)₂O (44.7 g, 0.2 mol) in MeCN (100 mL) was added. The mixture was warmed to room temperature and stirred overnight. After the evaporation of the MeCN, the residue was diluted with DCM (800 mL) and acidified with 1 M HCl to pH 2 at −5° C. The aqueous was extracted with DCM (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over Na₂SO₄ and concentrated to yield Compound 1 (66.5 g) as a white solid. LC-MS: 366 (M+Na), 709 (2M+Na).

To a solution of Compound 1 (66.5 g, 193 μmol), Meldrum's acid (33.4 g, 232 mmol) and DMAP (37.7 g, 309 mmol) in anhydrous DCM (600 mL), was added dropwise a solution of DCC (47.9 g, 232 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight. Crystals of dicyclohexylurea were observed. The mixture was filtered, washed with 5% KHSO₄ (5×200 mL) and saturated aqueous NaCl (200 mL), then dried over anhydrous MgSO₄ under refrigeration overnight. The solution was then evaporated to yield crude Compound 2 (91 g) as a light yellow solid. LC-MS: 492 (M+Na), 961 (2M+Na).

To a solution of crude Compound 2 (91 g, 193 mmol) in anhydrous DCM (1 L) was added AcOH (127.5 g, 2.1 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 30 minutes, then NaBH₄ (18.3 g, 483 mmol) was added in small portions over 1 hour. After stirring for another 1 hour at −5° C., saturated aqueous NaCl (500 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product, which was further purified by washing with Et₂O to yield Compound 3 (68 g) as a light yellow solid. LC-MS: 478 (M+Na), 933 (2M+Na).

A solution of Compound 3 (68 g, 149 mmol) in anhydrous toluene (500 mL) was refluxed under nitrogen for 3 hours. After evaporation of the solvent, the residue was purified by chromatography (hexanes:EtOAc=10:1) to yield the title compound (38 g) as a light yellow oil. LC-MS: 376 (M+Na), 729 (2M+Na).

Preparation 4 (2R,4R)-4-Amino-5-(4-bromophenyl)-2-hydroxypentanoic Acid Ethyl Ester

To a solution of (S)-2-(4-bromobenzyl)-5-oxopyrrolidine-1-carboxylic acid t-butyl ester (38 g, 107 mmol) in anhydrous DCM (250 mL) was added TFA (20 mL, 0.27 mol) at −5° C. under nitrogen. The mixture was warmed to room temperature and stirred overnight. After evaporation of the solvent, the residue was diluted with EtOAc (300 mL) and washed with saturated aqueous NaHCO₃ (3×200 mL), water (200 mL), saturated aqueous NaCl (250 mL), dried over Na₂SO₄ and concentrated to yield crude Compound 1 (24 g) as a light yellow solid. LC-MS: 254 [M+H].

To a solution of NaH (8.6 g, 250 mmol) in anhydrous THF (200 mL) was added dropwise a solution of Compound 1 (24 g, 94 mmol) in anhydrous THF (200 mL) over 30 minutes at 0° C. under nitrogen. The mixture was warmed to room temperature and stirred for 2 hours. After cooling to 0° C., pivaloyl chloride (18 g, 150 mmol) was added dropwise over 30 minutes. The mixture was warmed to room temperature and stirred overnight. The reaction was quenched with saturated aqueous NH₄Cl (300 mL) and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=25:1) to yield Compound 2 (18 g) as a light yellow solid. LC-MS: 360 (M+Na).

To a solution of Compound 2 (18 g, 53 mmol) in anhydrous THF (250 mL) was added dropwise NaHMDS (47.7 mL, 96 mmol) over 30 minutes at −78° C. under nitrogen. After stirring at −78° C. for 90 minutes, a solution of (+)-(8,8-dichlorocamphorylsulfonyl)-oxaziridine (31.6 g, 106 mmol) was added dropwise over 30 minutes. After stirring at −78° C. for 2 hours, the reaction was quenched with saturated aqueous NH₄Cl (400 mL) and extracted with EtOAc (3×300 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered, and concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=15:1) to yield Compound 3 (8.9 g) as a light yellow solid. LC-MS: 376 (M+Na).

A solution of Compound 3 (8.9 g, 25 mmol) in concentrated HCl (81 mL, 81 mmol) was heated at 100° C. for 16 hours. The mixture was then concentrated to yield the crude product which was further purified by washing with Et₂O to yield compound 4 (7 g) as a light yellow solid HCl salt. LC-MS: 323 (M+H).

A solution of compound 4 (7 g, 22 mmol) in EtOH (10 mL) was combined with 8M HCl in EtOH (120 mL, 960 mmol) at room temperature. The mixture was heated at 50° C. for 16 hours, then concentrated. The crude product was further purified by washing with Et₂O to yield the title compound (6 g) as a light yellow solid HCl salt. LC-MS: 352 (M+H).

Preparation 5 (3R,5R)-5-(3′-Chlorobiphenyl-4-ylmethyl)-1-(2,2-dimethylpropionyl)-3-hydroxypyrrolidin-2-one

To a solution of (S)-2-(4-bromobenzyl)-5-oxopyrrolidine-1-carboxylic acid t-butyl ester (15 g, 43 mmol) in 1,4-dioxane (600 mL) was added 3-chlorophenylboronic acid (8 g, 51 mmol) and Pd(dppf)₂Cl₂ (3.1 g, 4.2 mmol) at room temperature under nitrogen. After stirring for 10 minutes, a solution of K₂CO₃ (11.7 g, 85 mmol) in water (60 mL) was added. The mixture was heated to 60° C. and stirred overnight. After evaporation of the solvent, water (200 mL) was added and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (400 mL), dried over Na₂SO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=6:1) to yield Compound 1 (15 g) as a light yellow solid. LC-MS: 408 (M+Na).

To a solution of Compound 1 (15 g, 0.039 mol) in anhydrous DCM (250 mL) was added TFA (20 mL, 270 mmol) at −5° C. under nitrogen. The mixture was warmed to room temperature and stirred overnight. After evaporation of the solvent, the residue was diluted with EtOAc (300 mL), then washed with saturated aqueous NaHCO₃ (3×200 mL), water (200 mL), and saturated aqueous NaCl (250 mL), then dried over Na₂SO₄ and concentrated to yield crude Compound 2 (11 g) as a light yellow solid. LC-MS: 286 [M+H].

To a solution of NaH (2.3 g, 98 mmol) in anhydrous THF (200 mL) was added dropwise a solution of Compound 2 (11 g, 39 mmol) in anhydrous THF (100 mL) over 30 minutes at 0° C. under nitrogen. The mixture was warmed to room temperature and stirred for 2 hours. After cooling to 0° C., pivaloyl chloride (6 g, 51 mmol) was added dropwise over 30 minutes. The mixture was warmed to room temperature and stirred overnight. The reaction was quenched with saturated aqueous NH₄Cl (200 mL) and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product which was further purified by chromatography (hexanes:EtOAc=25:1) to yield Compound 3 (10.5 g) as a light yellow solid. LC-MS: 391 (M+Na).

To a solution of Compound 3 (10.5 g, 29 mmol) in anhydrous THF (120 mL) was added dropwise NaHMDS (29 mL, 58 mmol) over 30 minutes at −78° C. under nitrogen. After stirring at −78° C. for 90 minutes, a solution of (+)-(8,8-dichlorocamphorylsulfonyl)-oxaziridine (15.6 g, 52 mmol) was added dropwise over 30 minutes. After stirring at −78° C. for 2 hours, the reaction was quenched with saturated NH₄Cl (400 mL) and extracted with EtOAc (3×300 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered, and concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=15:1) to yield the title compound (9.6 g) as a light yellow solid. LC-MS: 408 (M+Na).

Preparation 6 (2R,4R)-4-Amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid Ethyl Ester

A solution of (3R,5R)-5-(3′-chlorobiphenyl-4-ylmethyl)-1-(2,2-dimethylpropionyl)-3-hydroxypyrrolidin-2-one (9.6 g, 25 mmol) in concentrated HCl (81 mL, 81 mmol) was heated at 100° C. for 16 hours. The mixture was then concentrated to give the crude product which was further purified by washing with Et₂O to yield Compound 1 (5.7 g) as a light yellow solid HCl salt. LC-MS: 320 (M+H).

To a solution of Compound 1 (5.7 g, 18 mmol) in EtOH (10 mL) was added 8M HCl in EtOH (120 mL, 960 mmol) at room temperature. The mixture was heated at 50° C. for 16 hours. After concentration, the crude product was further purified by washing with Et₂O to yield the title compound (2.1 g) as a light yellow solid HCl salt. LC-MS: 348 (M+H).

Preparation 7 (2R,4R)-4-Amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid

1 M aqueous HCl (2.0 mmol) was added to (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (150.0 mg, 431 μmol) and the mixture was stirred at 100° C. for 2 hours. The mixture was concentrated under vacuum for 3 hours and the residue was purified by reverse phase to yield the title compound (117 mg) as a white solid.

Preparation 8 Chloro-oxo-acetic Acid Isopropyl Ester

Isopropanol (158 μL, 2.1 mmol, 1.0 eq.) was added dropwise over 5 minutes to oxalyl chloride (350 μL, 414 μmol, 2.0 eq.) at 0° C., and the resulting mixture was stirred at room temperature for 2 hours. The excess oxalyl chloride was removed by rotary evaporation (40° C., 50 mmHg) and used without further purification.

Preparation 9 Chloro-oxo-acetic Acid Isobutyl Ester

Isobutanol (191 μL, 2.1 mmol, 1.0 eq.) was added dropwise over 5 minutes to oxalyl chloride (350 μL, 414 μmol, 2.0 eq.) at 0° C., and the resulting mixture was stirred at room temperature for 2 hours. The excess oxalyl chloride was removed by rotary evaporation (40° C., 40 mmHg) and used without further purification.

Preparation 10 t-Butyl Oxalyl Chloride

Oxalyl chloride (274 μL, 3.2 mmol) was added to a solution of t-butyl alcohol (289 μL, 3.0 mmol) in ether (2.0 mL, 19.0 mmol) and the mixture was stirred at room temperature for 1 hour and then concentrated in vacuo to yield a clear colorless liquid. An approximately 1M solution of t-butyl oxalyl chloride was prepared by dissolving the resulting clear colorless liquid in DCM (˜3.0 mL).

Preparation 11 Chloro-oxo-acetic Acid 2-Methoxyethyl Ester

A solution of 2-methoxyethanol (295 mg, 3.9 mmol) in DCM (total volume: 0.5 mL) was added to a solution of oxalyl chloride (0.5 mL, 5.8 mmol) in DCM (total volume 1.0 mL) at 0° C. and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo and the resulting residue was dissolved in DCM (3.9 mL) to yield a 1.0M solution in DCM.

Preparation 12 Chloro-oxo-acetic Acid 3-Ethoxypropyl Ester

A solution of 3-ethoxypropan-1-ol (404 mg, 3.9 mmol) in DCM (total volume: 0.5 mL) was added to a solution of oxalyl chloride (0.5 mL, 5.8 mmol) in DCM (total volume 1.0 mL) at 0° C. and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo and the resulting residue was dissolved in DCM (3.9 mL) to yield a 1.0M solution in DCM.

Preparation 13 Chloro-oxo-acetic Acid 2-Phenoxyethyl Ester

A solution of 2-phenoxyethanol (536 mg, 3.9 mmol) in DCM (total volume: 0.5 mL) was added to a solution of oxalyl chloride (0.5 mL, 5.8 mmol) in DCM (total volume 1.0 mL) at 0° C. and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo and the resulting residue was dissolved in DCM (3.9 mL) to yield a 1.0M solution in DCM.

Preparation 14 (2R,4R)-4-t-Butoxycarbonylamino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid

A solution of (3R,5R)-5-(3′-chlorobiphenyl-4-ylmethyl)-1-(2,2-dimethylpropionyl)-3-hydroxypyrrolidin-2-one (4.5 g, 11.7 mmol) in concentrated HCl (30 mL) was stirred at 100° C. for 16 hours. The mixture was concentrated in vacuo to yield Compound 1 (4 g) as a white solid HCl salt. LC-MS: 321 [M+H]⁺.

To a solution of NaOH (1.8 g, 45.2 mmol) in water (100 mL), was added Compound 1 (4 g, 11.3 mmol) in MeCN (100 mL) dropwise. The mixture was stirred for 10 minutes at 0° C. Di-t-butyldicarbonate (7.17 g, 33.8 mmol) was added and the mixture was stirred for 15 hours at room temperature. The resulting mixture was concentrated in vacuo to remove MeCN, then diluted with DCM (300 mL), and the pH adjusted to pH=5-6 with 1N aqueous HCl. Then the organic layer was collected and the residue was extracted with DCM (3×300 mL). The combined organic layers were concentrated and washed with hexanes (150 mL) to yield the title compound (4 g) as a white solid. LC-MS: 442 [M+Na]⁺.

Preparation 15 (2R,4R)-4-Amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid 2,2,3,3,3-pentafluoropropyl Ester

To a solution of (2R,4R)-4-t-Butoxycarbonylamino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid (0.9 g, 6 mmol) and 2,2,3,3,3-pentafluoropropan-1-ol (450 mg, 3 mmol) in DCM (30 mL) was added DCC (880 mg, 4.3 mmol) and DMAP (260 mg, 2.1 mmol). The resulting mixture was stirred for 15 hours at room temperature, then concentrated in vacuo. The residue was dissolved in EtOAc (100 mL) and washed with water (30 mL) and saturated aqueous NaCl (30 mL). The organic layer was collected and concentrated and purified by column chromatography (hexanes/EtOAc=5:1) to yield Compound 3 (0.4 g) as a white solid. LC-MS: 574 [M+Na]⁺.

A solution of Compound 3 (0.4 g, 690 μmol) in 1.4 M HCl in a 1,4-dixoane solution (15 mL) was stirred overnight, and then concentrated in vacuo. The residue was dispersed in EtOAc (10 mL), and the precipitate was collected by filtration to yield the title compound as an off-white solid HCl salt (165 mg). LC-MS: 452 [M+H]⁺. ¹H NMR: (DMSO-d₆) 1.95-1.82 (m, 2H), 2.99-2.98 (m, 2H), 3.56 (br, 1H), 4.41-4.38 (m, 1H), 4.92-4.82 (m, 2H), 6.35 (s, 1H), 7.71-7.38 (m, 8H), 8.09 (s, 3H).

Preparation 16 (2R,4R)-4-Amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid 5-Methyl-2-oxo[1,3]dioxol-4-ylmethyl Ester

A suspension of (2R,4R)-4-t-butoxycarbonylamino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid (740 mg, 1.8 mmol), 4-(bromomethyl)-5-methyl-1,3-dioxol-2-one (340 mg, 1.8 mmol), potassium iodide (58 mg, 350 μmol), and K₂CO₃ (486 mg, 3.5 mmol) in DMF (20 mL) was stirred for 4 hours at room temperature. The mixture was diluted with EtOAc (150 mL) and washed with water (30 mL). The organic layer was collected and concentrated and purified by column chromatography (hexanes/EtOAc=1:1) to yield a white solid (490 mg). LC-MS: 554 [M+23]⁺. A solution of this solid (476 mg, 890 μmol) in 3 N HCl in 1,4-dioxane (20 mL) was stirred overnight, and then concentrated in vacuo. The residue was dispersed in EtOAc (10 mL), and the precipitate was collected by filtration to yield the title compound as an off-white solid (290 mg). LC-MS: 432 [M+H]⁺. ¹H NMR: (DMSO-d₆) 1.92-1.82 (m, 2H), 2.16 (s, 3H), 2.99 (br, 2H), 3.56 (br, 1H), 4.35-4.32 (m, 1H), 5.017 (s, 2H), 6.17 (s, 1H), 7.39-7.36 (m, 4H), 7.71-7.68 (m, 4H), 8.05 (s, 3H).

Preparation 17 (2R,4R)-4-Amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid Butyryloxymethyl Ester

A solution of (2R,4R)-4-t-butoxycarbonylamino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid (900 mg, 2.1 mmol), chloromethyl butyrate (350 mg, 2.6 mmol), sodium iodide (481 mg, 3.21 mmol) and DIPEA (828 mg, 6.42 mmol) in DMF (20 mL) was stirred for 16 hours at 30° C. The mixture was diluted with EtOAc (150 mL) and washed with water (50 mL) and saturated aqueous NaCl (50 mL). The organic layer was collected and concentrated and purified by column chromatography (hexanes/EtOAc=5:1) to yield a white solid (240 mg). LC-MS: 542 [M+Na]⁺. A solution of this solid (240 mg, 460 μmol) in 1.4 M HCl in 1,4-dixoane (15 mL) was stirred overnight, and then concentrated in vacuo. The residue was dispersed in EtOAc (10 mL), and the precipitated was collected by filtration to yield the title compound as an off-white solid HCl salt (140 mg). LC-MS: 420 [M+H]⁺. ¹H NMR: (DMSO) 0.85 (t, J=7.5 Hz, 3H), 1.61-1.52 (m, 2H), 1.89-1.86 (m, 2H), 2.30 (t, J=7.5 Hz, 2H), 2.98 (br, 2H), 3.56 (br, 1H), 4.33-4.30 (m, 1H), 5.74-5.68 (m, 2H), 6.21 (s, 1H), 7.37-7.35 (m, 4H), 7.70-7.767 (m, 4H), 8.01 (brs, 3H).

Preparation 18 (2R,4R)-4-Amino-5-(2′,5′-dichlorobiphenyl-4-yl)-2-hydroxypentanoic Acid Ethyl Ester

To a solution of (S)-2-(4-bromobenzyl)-5-oxopyrrolidine-1-carboxylic acid t-butyl ester (33.5 g, 95 mmol) in 1,4-dioxane (1.2 L) was added 2,5-dichlorophenylboronic acid (21.7 g, 114 mmol) and Pd(dppf)₂Cl₂ (3.5 g, 4.7 mmol) at room temperature under nitrogen. After stirring for 10 minutes, a solution of K₂CO₃ (26.1 g, 189 mmol) in water (120 mL) was added. The mixture was heated to 60° C. and stirred overnight. After evaporation of the solvent, water (400 mL) was added and extracted with EtOAc (3×400 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over anhydrous Na₂SO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=6:1) to yield Compound 1 (35.8 g) as a light yellow solid. LC-MS: 442 [M+Na].

To a solution of Compound 1 (35.8 g, 85 mmol) in anhydrous DCM (300 mL) was added TFA (30 mL, 405 mmol) at −5° C. under nitrogen. The mixture was warmed to room temperature and stirred overnight. After evaporation of the solvent, the residue was diluted with EtOAc (500 mL), then washed with saturated aqueous NaHCO₃ (3×300 mL), water (200 mL), and saturated aqueous NaCl (250 mL), then dried over Na₂SO₄ and concentrated to yield crude Compound 2 (26 g) as a light yellow solid. LC-MS: 320 [M+H].

To a solution of Compound 2 (26 g, 81 mmol) in anhydrous THF (500 mL) was added dropwise n-BuLi in hexane (39 mL, 97 mmol) over 1 hour at −78° C. under nitrogen. After stirring at −78° C. for 2 hours, the reaction was quenched by adding pivaloyl chloride (12.7 g, 105 mmol) dropwise over 30 minutes. After stirring at −78° C. for 2 hours, the reaction was quenched with saturated aqueous NH₄Cl (200 mL) and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over anhydrous MgSO₄, filtered and concentrated to yield the crude product which was further purified by chromatography (hexanes:EtOAc=25:1) to yield Compound 3 (33 g) as a light yellow solid. LC-MS: 426 [M+Na].

To a solution of Compound 3 (10 g, 0.025 mol) in anhydrous THF (120 mL) was added dropwise NaHMDS (18.6 mL, 37 mmol) over 30 minutes at −78° C. under nitrogen. After stirring at −78° C. for 2 hours, a solution of (+)-(8,8-dichlorocamphorylsulfonyl)-oxaziridine (11.1 g, 37 mmol) in THF (80 mL) was added dropwise over 30 minutes. After stirring at −78° C. for 2 hours, the reaction was quenched with saturated aqueous NH₄Cl (500 mL) and extracted with EtOAc (3×300 mL). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered and concentrated to yield the crude product which was further purified by chromatography (hexanes:EtOAc=15:1) to yield Compound 4 (4.2 g) as a light yellow oil. LC-MS: 442 [M+Na].

A solution of Compound 4 (4.2 g, 10 mmol) in concentrated HCl (80 mL, 0.96 mol) was heated at 100° C. for 16 hours. The mixture was then concentrated to yield crude the product which was further purified by washing with Et₂O to yield Compound 5 (3.8 g) as a white solid. LC-MS: 354 [M+H].

To a solution of Compound 5 (3.8 g, 10 mmol) in EtOH (5 mL) was added 4M HCl in EtOH (100 mL, 0.4 mol) at room temperature. The mixture was heated at 50° C. for 16 hours. After concentration, the crude product which was further purified by washing with Et₂O to yield the title compound (3.3 g) as a white solid. LC-MS: 382 [M+H].

Preparation 19 (3R,5R)-5-Amino-6-(4-bromo-2-chlorophenyl)-2-ethoxyhex-1-en-3-ol

To a suspension of 4-bromo-2-chlorobenzaldehyde (50 g, 22.8 mmol) in MeOH (500 mL) was added NaBH₄ (17.3 g, 45.6 mmol) in portions at 0° C. The mixture was stirred for 30 minutes and then aqueous NH₄Cl was added to quench the reaction. The mixture was concentrated in vacuo. The residue was extracted with EtOAc (2×200 mL) and the combined organic layers were dried over anhydrous Na₂SO₄, and concentrated under vacuum to yield Compound 1 (48 g) as a white solid.

To a solution of Compound 1 (46.8 g, 21.1 mmol) in dry DCM (500 mL) was added phosphorous tribromide (68.6 g, 25.3 mmol) dropwise at 0° C. under nitrogen. The mixture was stirred for 2 hours and then washed with saturated aqueous NaHCO₃ (2×200 mL) and saturated aqueous NaCl (200 mL), dried over anhydrous Na₂SO₄, concentrated under vacuum to yield Compound 2 (36 g) as a colorless oil.

To a stirred solution of (R)-pyrrolidine-2-carboxylic acid (57.7 g, 0.5 mol) and KOH (84 g, 1.5 mol) in isopropyl alcohol (330 mL) was added benzyl chloride (70 mL, 0.6 mol) dropwise at 0° C. over 3 hours. The mixture was then stirred overnight at the same temperature. The resulting mixture was neutralized with concentrate HCl to pH=6, followed by the addition of chloroform (200 mL). The mixture was stirred for 30 minutes, then filtered and the precipitate was washed with chloroform (3×100 mL). The combined chloroform solutions were dried over anhydrous Na₂SO₄, and concentrated under vacuum to yield Compound 3 (52 g) as a white solid. LC-MS: 206 [M+H]⁺.

To a solution of Compound 3 (10 g, 48.8 mmol) in dry DCM (50 mL) was added SO₂Cl₂ (7.3 g, 61 mmol) at −20° C. under nitrogen. The mixture was stirred at −20° C. for 3 hours followed by the addition of a solution of (2-aminophenyl)(phenyl)methanone (6 g, 30.5 mmol) in dry DCM (25 mL) and the mixture was stirred overnight at room temperature. A solution of Na₂CO₃ (10.3 g) in water (40 mL) was added at 0° C. The organic layer was separated and the aqueous layer was extracted with DCM (50 mL×3). The combined organic layers were dried over anhydrous Na₂SO₄ and concentrated under vacuum. The residue was washed with MTBE (2×50 mL) to yield Compound 4 (8.5 g) as a yellow solid. LC-MS: 385 [M+H]⁺.

To a solution of Compound 4 (29.4 g, 76.5 mmol), glycine (28.7 g, 382.4 mmol) and Ni(NO₃)₂.6H₂O (44.5 g, 152.9 mmol) in MeOH (280 mL) was added a solution of KOH (30 g, 535.3 mmol) in MeOH (100 mL) at 45° C. under nitrogen. The mixture was stirred at 60° C. for an hour. The resulting solution was neutralized with AcOH (31 mL) and poured into ice water (380 mL). The resulting solid was filtered and dissolved in DCM (450 mL), which was washed with saturated aqueous NaCl (150 mL), dried over anhydrous Na₂SO₄ and concentrated. The residue was washed with EtOAc (2×50 mL) to yield compound 5 (38 g) as a red solid. LC-MS: 498 [M+H]⁺.

Compound 5 (14.3 g, 28.7 mmol) and NaOH (3.4 g, 81.6 mmol) were added to a flask which was purged with nitrogen twice. Anhydrous DMF (100 mL) was added and the mixture was stirred for 5 minutes at 0° C. before a solution of compound 2 (8.6 g, 30.1 mmol) in DMF (20 mL) was added. The reaction mixture was stirred at room temperature for 30 minutes until complete consumption of compound 4 (checked by TLC). The resulting mixture was poured into a 5% AcOH aqueous solution (120 mL) which was then extracted with DCM (3×150 mL) and the combined organic layers were washed with saturated aqueous NaCl (150 mL), dried over anhydrous Na₂SO₄ and concentrated under vacuum. The residue was recrystallized with DCM/Et₂O (1:1) to yield Compound 6 (15.5 g) as a red solid. LC-MS: 702 [M+H]⁺.

To a solution of Compound 6 (46 g, 65.6 mmol) in MeOH (300 mL) was added 3N HCl (200 mL). The mixture was refluxed until the red color turned green. The resulting solution was concentrated under vacuum and concentrated NH₃.H₂O (100 mL) was added, and followed by the extraction with DCM (2×200 mL). The aqueous phase was concentrated under vacuum and subjected to the cation exchange resin (eluted with NH₃.H₂O/EtOH, 1:1) to yield Compound 7 (15 g) as a white solid. LC-MS: 280 [M+H]⁺.

To a suspension of Compound 7 (15 g, 53.9 mmol) in MeCN (150 mL) was added a solution of NaOH (4.3 g, 107.7 mmol) in water (150 mL) at 0° C., and followed by the addition of (BOC)₂O (17.6 g, 80.8 mmol). The mixture was stirred overnight at room temperature. The resulting solution was concentrated under vacuum, followed by the extraction with DCM (2×150 mL). The aqueous phase was acidified with 1N HCl to pH=3 and extracted with EtOAc (3×150 mL). The combined organic layers were washed with saturated aqueous NaCl (150 mL), dried over anhydrous Na₂SO₄ and concentrated under vacuum to yield Compound 8 (12.3 g, 60%) as a white solid. LC-MS: 402 [M+Na]⁺. To a suspension of Compound 8 (18.4 g, 48.5 mmol) and Meldrum's acid (8.4 g, 58.2 mmol) in DCM (400 mL) was added DMAP (9.5 g, 77.6 mmol) at −5° C. After stirring for 10 minutes, a solution of DCC (12 g, 58.2 mmol) in DCM (100 mL) was added dropwise at −5° C. The mixture was stirred overnight at room temperature. The resulting solution was cooled to 0° C. and filtered. The filtrate was washed with aqueous citric acid (3×200 mL) and saturated aqueous NaCl (200 mL), dried over anhydrous Na₂SO₄, and concentrated under vacuum. The residue was washed with Et₂O (2×50 mL) to yield Compound 9 (22 g) as a light yellow solid.

To a solution of Compound 9 (22 g, 43.6 mmol) in DCM (400 mL) was added AcOH (28.8 g, 479.4 mmol) at 0° C. After stirring for 10 minutes, NaBH₄ (4.1 g, 109 mmol) was added in portions. The mixture was stirred for an hour at 0° C. The resulting solution was washed with saturated aqueous NaHCO₃ (2×200 mL) and saturated aqueous NaCl (200 mL), dried over anhydrous Na₂SO₄ and concentrated under vacuum. The residue was washed with ether (2×100 mL) to yield Compound 10 (18.6 g) as an off-white solid. LC-MS: 514 [M+Na]⁺.

A solution of Compound 10 (18.6 g, 37.9 mmol) in toluene (350 mL) was heated under reflux for 2 hours. Upon cooling, the mixture was evaporated to dryness to yield Compound 11 (14 g) as a yellow syrup. LC-MS: 334 [M-tBu+H]⁺.

To a solution of Compound 11 (14 g, 36.0 mmol) in DCM (250 mL) was added TFA (20 mL). The mixture was stirred for 4 hours at 0° C. The resulting solution was concentrated under vacuum to remove TFA. The residue was dissolved in DCM (400 mL) and washed with saturated aqueous NaHCO₃ (2×200 mL), dried over anhydrous Na₂SO₄ and concentrated to yield Compound 12 (10 g) as a yellow solid. LC-MS: 290 [M+H]⁺.

To a solution of Compound 12 (10 g, 34.7 mmol) in dry THF (250 mL) was added NaH (2.4 g, 69.3 mmol, 70%) at 0° C. The mixture was stirred for one hour at 0° C. under nitrogen. Then pivaloyl chloride (5 g, 41.6 mmol) was added. After stirring for another 2 hours, saturated aqueous NaHCO₃ (100 mL) was added to quench the reaction. The resulting mixture was concentrated and extracted with EtOAc (3×100 mL) and the combined organic layers were washed with saturated aqueous NaCl (100 mL), dried over anhydrous Na₂SO₄ and concentrated under vacuum. The residue was purified by silica gel chromatography (hexanes/EtOAc, 5:1) to yield Compound 13 (11.8 g) as a white solid. LC-MS: 374[M+H]⁺.

To a solution of Compound 13 (11.8 g, 31.8 mmol) in dry THF (70 mL) was added NaHMDS (24 mL, 47.7 mmol, 2.0 M in THF) dropwise at −78° C. under nitrogen. After stirring for 30 minutes, a solution of (+)-(8,8-dichlorocamphorylsulfonyl)oxaziridine (15.2 g, 50.8 mmol) in THF (70 mL) was added dropwise at −78° C. The mixture was stirred for another hour at the same temperature before aqueous NH₄Cl (70 mL) was added to quench the reaction. The resulting mixture was extracted with EtOAc (3×150 mL) and the combined organic layers were washed with saturated aqueous NaCl (150 mL), dried over anhydrous Na₂SO₄, concentrated under vacuum and purified by silica gel chromatography (hexanes/EtOAc, 20:1-5:1) to yield the crude product (5 g), which was further purified by preparative HPLC to yield Compound 14 (4 g) as a yellow solid. LC-MS: 390 [M+H]⁺.

A solution of Compound 14 (4 g, 10.3 mmol) in concentrated HCl (50 mL) was heated under reflux overnight. The mixture was concentrated under vacuum and the resulting solid was washed with Et₂O (2×50 mL) to yield Compound 15 (3.1 g) as a white solid HCl salt. LC-MS: 324 [M+H]⁺.

A solution of Compound 15 (3.1 g, 8.6 mmol) in HCl/EtOH (6.7M, 40 mL) was stirred overnight at 50° C. The resulting mixture was concentrated under vacuum and the residue was washed with ether (2×50 mL) to yield the title compound (2.9 g) as an off-white solid HCl salt. LC-MS: 352 [M+H]⁺. ¹H NMR: (CD₃OD) 1.268 (t, J=6.9 Hz, 3H), 1.862-1.946 (m, 1H), 2.068-2.143 (m, 1H), 3.104-3.199 (m, 2H), 3.769-3.809 (m, 1H), 4.162-4.209 (m, 2H), 4.274-4.881 (m, 1H), 7.325 (dd, J=8.1, 2.1 Hz, 1H), 7.522 (dd, J=8.3, 3.0 Hz, 1H), 7.696 (d, J=1.8 Hz, 1H).

Preparation 20 [(R)-1-Biphenyl-4-ylmethyl-2-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-2-oxoethyl]carbamic Acid t-Butyl Ester

To a solution of (R)-3-biphenyl-4-yl-2-t-butoxycarbonylamino-propionic acid (50 g, 146 mmol), Meldrum's acid (23.3 g, 161 mmol) and DMAP (27.8 g, 227 mmol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 161 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL) and saturated aqueous NaCl (1×200 mL), then dried under refrigeration with MgSO₄ overnight. The solution was evaporated to yield the title compound (68 g, light yellow solid), which was used without further purification. LC-MS: 490 [M+Na], 957 [2M+Na].

Preparation 21 (2R,4S)-5-biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethylpentanoic Acid Ethyl Ester (compound 6) and (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethylpentanoic Acid Ethyl Ester (compound 7)

To a solution of crude [(R)-1-biphenyl-4-ylmethyl-2-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-2-oxoethyl]carbamic acid t-butyl ester (68 g, 147 mmol) in anhydrous DCM (1 L) was added AcOH (96.7 g, 1.6 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (13.9 g, 366 mmol) was added in small portions over 1 hour. After stirring for another 1 hour at −5° C., saturated aqueous NaCl (300 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over MgSO₄, filtered, and evaporated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=5:1) to yield Compound 1 (46 g, light yellow solid). LC-MS: 476 [M+Na], 929 [2M+Na].

A solution of Compound 1 (46 g, 101 mmol) in anhydrous toluene (300 mL) was refluxed under nitrogen for 3 hours. After evaporation of the solvent, the residue was purified by chromatography (hexanes:EtOAc=10:1) to yield Compound 2 (27 g, light yellow solid). LC-MS: 374 [M+Na], 725 [2M+Na]. ¹H NMR (300 MHz, CDCl3): δ7.64-7.62 (m, 4H), 7.51-7.46 (m, 2H), 7.42-7.39 (m, 1H), 7.39-7.30 (m, 2H), 4.50-4.43 (m, 1H), 3.27-3.89 (m, 1H), 2.88-2.80 (m, 1H), 2.48-2.42 (m, 2H), 2.09-1.88 (m, 2H), 1.66 (s, 9H).

A mixture of Compound 2 (27 g, 77 mmol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (40.3 g, 231 mmol) was heated to 80° C. under nitrogen. After stirring for 3 hours at 80° C., the mixture was diluted with EtOAc (300 mL), washed with water (2×150 mL) and saturated aqueous NaCl (2×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 3 (29.7 g, light yellow oil). LC-MS: 425 [M+H], 835 [2M+H].

To a solution of crude Compound 3 (29.7 g, 73 mmol) in THF (200 mL) was added 1 M HCl (81 mL) at 0° C. under nitrogen. After stirring for 1 hour at room temperature, the mixture was diluted with EtOAc (100 mL) and adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layer was extracted with EtOAc (2×150 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 4 (29.4 g, yellow oil). LC-MS: 402 [M+Na], 781 [2M+Na].

To a solution of Compound 4 (29.4 g, 77 mmol) in anhydrous THF (300 mL) was added anhydrous EtOH (30 mL) and AcOH (92.5 g, 1.5 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₃CN (19.4 g, 308 mmol) was added in small portions over 1 hour. After stirring for one additional hour at −5° C., the mixture was adjusted with saturated aqueous NaHCO₃ to pH 7. The aqueous layers were extracted with EtOAc (2×200 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (1×150 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=5:1) to yield Compound 5 (11.2 g, light yellow solid). LC-MS: 404 [M+Na], 785 [2M+Na].

To a solution of Compound 5 (11.2 g, 29 mmol) in anhydrous EtOH (500 mL) was added anhydrous K₂CO₃ (8.0 g, 58 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred for 16 hours. After filtration, the filtrate was concentrated and the residual was diluted with water (150 mL), DCM (200 mL) and saturated aqueous NaCl (50 mL). After separation, the aqueous layer was extracted with DCM (2×150 mL). The combined organic layers were washed with saturated aqueous NaCl (2×200 mL), dried over MgSO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=5:1) to yield Compounds 6 and 7 (8.3 g, light yellow solid).

Compound 6: LC-MS: 450 [M+Na], 877 [2M+Na]. ¹H NMR (300 MHz, CDCl3): δ7.58-7.23 (m, 9H), 4.46-4.43 (d, 1H), 4.20-4.13 (m, 2H), 3.94 (s, 1H), 3.82-3.70 (m, 2H), 2.85-2.70 (m, 3H), 2.25-2.22 (d, 1H), 2.01-1.92 (m, 1H), 1.47 (s, 9H), 1.26-1.24 (m, 3H).

Compound 7: LC-MS: 450 [M+Na], 877 [2M+Na]. ¹H NMR (300 MHz, CDCl3): δ7.58-7.55 (m, 4H), 7.50-7.43 (m, 2H), 7.40-7.30 (m, 1H), 7.26-7.23 (m, 1H), 4.46 (m, 1H), 4.21-4.13 (m, 2H), 3.94 (m, 1H), 3.82-3.77 (m, 2H), 2.83-2.81 (d, 2H), 2.66-2.63 (m, 1H), 2.24 (m, 1H), 1.83-1.81 (m, 2H), 1.38 (s, 9H), 1.30-1.25 (m, 3H).

Preparation 22 (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethylpentanoic Acid (R⁷=H; P²=BOC) and (2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethylpentanoic Acid Ethyl Ester (R⁷=—CH₂CH₃; P² removed)

(2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (210 mg) was saponified with LiOH to yield the BOC-protected acid (R⁷=H; P²=BOC) (120 mg). (2S,4S)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-pentanoic acid ethyl ester (˜180 mg) was subjected to HCl deprotection to yield the amine ester (R⁷=—CH₂CH₃; P² removed) as an HCl salt (120 mg).

Preparation 23 (2S,4S)-4-Amino-5-(2′-fluorobiphenyl-4-yl)-2-hydroxymethylpentanoic Acid Ethyl Ester

To a solution of (S)-2-(4-bromobenzyl)-5-oxopyrrolidine-1-carboxylic acid t-butyl ester (18.4 g, 52 mmol) in 1,4-dioxane (500 mL) was added 2-fluorophenylboronic acid (8.7 g, 63 mmol) and Pd(dppf)₂Cl₂ (3.8 g, 5.2 mmol) at room temperature under nitrogen. After stirring for 10 minutes, a solution of K₂CO₃ (14.4 g, 104 mmol) in water (50 mL) was added. The mixture was heated to 80° C. and stirred at this temperature for 5 hours. After evaporation of the solvent, water (300 mL) was added and the mixture was extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (400 mL), dried over Na₂SO₄ and concentrated to give the crude product which was further purified by column chromatography (hexanes:EtOAc=8:1) to yield Compound 1 (17.3 g) as a red oil. LC-MS: 392 [M+Na].

A mixture of Compound 1 (17.3 g, 46.7 m mol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (24.4 g, 140 mmol) was heated to 80° C. under nitrogen. After stirring for 3 hours at 80° C., the mixture was diluted with EtOAc (300 mL) and washed with water (2×150 mL), saturated aqueous NaCl (150 mL), dried over MgSO₄, filtered, and evaporated to yield crude Compound 2 (20.6 g) as a red oil. LC-MS: 425 [M+H], 849 (2M+H).

To a solution of crude Compound 2 (20.6 g, 48.6 mmol) in THF (300 mL), was added 1 M HCl (58 mL, 58 mmol) at 0° C. under nitrogen. After stirring for 1 hour at room temperature, the mixture was diluted with EtOAc (100 mL) and adjusted with saturated aqueous NaHCO₃ to a pH of 7. The aqueous layer was extracted with EtOAc (2×150 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (150 mL), dried over MgSO₄, filtered, and evaporated to yield the crude Compound 3 (18.9 g) as a red oil. LC-MS: 420 (M+Na), 817 (2M+Na).

To a solution of crude Compound 3 (18.9 g, 47.6 mmol) in anhydrous THF (400 mL) was added anhydrous EtOH (50 mL) and AcOH (57.2 g, 952 mmol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 30 minutes, then NaBH₃CN (15 g, 238 mmol) was added in small portions over 1 hour. After stirring for an additional 1 hour at −5° C., the mixture was adjusted with saturated aqueous NaHCO₃ to a pH of 7. The aqueous layer was extracted with EtOAc (3×200 mL) and the combined organic layers were washed with water (2×150 mL) and saturated aqueous NaCl (150 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product which was further purified by chromatography (hexanes:EtOAc=6:1) to yield Compound 4 (7.1 g) as a light yellow solid. LC-MS: 422 (M+Na), 821 (2M+Na).

To a solution of Compound 4 (7.1 g, 17.7 mmol) in anhydrous EtOH (500 mL) was added anhydrous K₂CO₃ (9.8 g, 70.8 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred for 16 hours. After filtration, the filtrate was concentrated and the residual was diluted with water (150 mL), DCM (200 mL) and saturated aqueous NaCl (50 mL). After separation, the aqueous layer was extracted with DCM (2×150 mL). The combined organic layers were washed with saturated aqueous NaCl (2×200 mL), dried over MgSO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=5:1) to yield Compound 5 (2 g) as a light yellow solid. 2.1 g of the (R,S) isomer was also obtained as a light yellow solid.

Compound 5 (400 mg, 0.9 mmol) was dissolved in MeCN (3 mL) and 4 M HCl in dioxane (0.5 mL). The mixture was stirred at room temperature for 1 hour then concentrated to yield the title compound as an HCl salt (340 mg), which was formed as an oil and solidified overnight.

Preparation 24 [(R)-2-Biphenyl-4-yl-1-(2,2,5-trimethyl-4,6-dioxo-1,3-dioxinan-5-ylmethyl)ethyl]carbamic Acid t-Butyl Ester

AcOH (8.6 mL) was added to a solution of crude [(R)-1-biphenyl-4-ylmethyl-2-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-2-oxo-ethyl]-carbamic acid t-butyl ester (6.4 g, 14 mmol) in anhydrous MeCN (90 mL) was added AcOH (8.6 mL) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 30 minutes, then sodium borohydride (1.3 g, 34.5 mmol) was added in small portions over 2 hours. After stirring for another 1 hour at −5° C., saturated aqueous NaCl and 1.7 M of NaCl in water (30 mL) was added. The layers were separated and the organic layer was washed with saturated aqueous NaCl (2×30 mL) and water (2×30 mL), dried under MgSO₄, filtered and evaporated. The resulting crude product was further purified by chromatography (5:1 heptane:EtOAc) to yield [(S)-2-biphenyl-4-yl-1-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-ylmethyl)ethyl]carbamic acid t-butyl ester (1.1 g, purity 98.4%) as a light yellow solid.

[(S)-2-Biphenyl-4-yl-1-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-ylmethyl)-ethyl]carbamic acid t-butyl ester (5.0 g, 11 mmol) and K₂CO₃ (1.8 g, 13.2 mmol) were dissolved in DMF (33.9 mL) and cooled to 0° C. with stirring under nitrogen. Methyl iodide (892 μL) was added and the resulting mixture was stirred at 0° C. for 1 hour. The mixture was allowed to warm to room temperature. Saturated aqueous NaCl (35 mL) and EtOAc (35 mL) were added, and the resulting mixture was stirred for 2 minutes. The layers were separated and the organic layer was evaporated. The residue was triturated with EtOAc (20 mL). The solid was filtered off and dried under vacuum. The filtrate was concentrated and triturated again with EtOAc to yield the title compound (3.9 g).

Preparation 25 (2S,4R)-5-Biphenyl-4-yl-4-t-butoxycarbonylamino-2-hydroxymethyl-2-methylpentanoic Acid (P²=BOC) and (2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methylpentanoic Acid (P² removed)

Distilled Water (140 mL) was purged 30 minutes under nitrogen, then cannulated into a vessel containing 0.1 M of samarium diiodide in THF (800 mL), exercising caution not to allow any air to come into contact with solution. While maintaining an atmosphere of nitrogen, a degassed solution of [(R)-2-biphenyl-4-yl-1-(2,2,5-trimethyl-4,6-dioxo-1,3-dioxinan-5-ylmethyl)ethyl]carbamic acid t-butyl ester (3.7 g, 8.0 mmol) and THF (100 mL) was added via canula. The resulting mixture was stirred for 15 minutes, then exposed to air. Saturated aqueous NaCl (12 mL), 10% citric acid (6 mL), and EtOAc (30 mL) were added. The mixture was stirred for 5 minutes, then both layers were extracted. The organic layer was dried over Na₂SO₄ and concentrated under vacuum. The crude product was purified by chromatography (330 g gold column, 50% EtOAc with 0.5% AcOH/ether gradient) to yield the BOC-protected acid. (P²=BOC) (1.4 g). The BOC-protected acid was dissolved in MeCN (10 mL), followed by the addition of 4N HCl in dioxane (10 mL). The solvent was evaporated and the product azeotroped with toluene (2×) to yield the acid. (P² removed) (1.0 g).

Preparation 26 (2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methylpentanoic Acid Ethyl Ester

(2S,4R)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methylpentanoic acid (0.3 g, 957 μmol) was combined with EtOH (6 mL) and 4 M of HCl in 1,4-dioxane (718 μL), and stirred overnight. The solvents were evaporated and the product was azeotroped with toluene (2×) to yield the title compound (295 mg), which was used without further purification.

Preparation 27 [(R)-1-(3′-Fluorobiphenyl-4-ylmethyl)-2-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-ethyl]carbamic Acid t-Butyl Ester

To a solution of (R)-2-amino-3-(4-bromophenyl)propionic acid (50 g, 0.2 mol) in MeCN (700 mL) was added a solution of NaOH (16.4 g, 0.4 mol) in water (700 mL) at −5° C. After stirring for 10 minutes, a solution of (BOC)₂O (44.7 g, 0.2 mol) in MeCN (100 mL) was added. The mixture was warmed to room temperature and stirred overnight. After evaporation of the MeCN, the residue was diluted with DCM (800 mL) and acidified with 1 M HCl to pH 2 at −5° C. The aqueous layer was extracted with DCM (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over anhydrous Na₂SO₄ and concentrated to yield Compound 1 (64.2 g, white solid). LC-MS: 366 [M+Na], 709 [2M+Na].

To a solution of Compound 1 (64.2 g, 187 mmol) in 1,4-dioxane (500 mL) was added 3-fluorophenylboronic acid (31.3 g, 224 mmol) and Pd(dppf)₂Cl₂ (13.7 g, 19 mmol) at room temperature under nitrogen. After stirring for 10 min, a solution of K₂CO₃ (51.7 g, 374 mmol) in water (250 mL) was added. The mixture was heated to 100° C. and stirred overnight. After evaporation of the solvent, water (200 mL) was added. The aqueous layer was acidified with 1 M HCl to pH 2 and extracted with EtOAc (3×200 mL). The combined organic layers were washed with saturated aqueous NaCl (400 mL), dried over anhydrous Na₂SO₄, and concentrated to yield the crude product which was further purified by column chromatography (hexanes:EtOAc=4:1) to yield Compound 2 (45 g, light yellow oil). LC-MS: 382 [M+Na], 741 [2M+Na].

To a solution of Compound 2 (45 g, 125 mmol), Meldrum's acid (23.5 g, 163 mmol), and DMAP (26.0 g, 213 mmol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 163 mmol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL) and saturated aqueous NaCl (1×200 mL), then dried under refrigeration with anhydrous MgSO₄ overnight. The solution was evaporated to yield the crude Compound 3 (57.7 g, light yellow oil). LC-MS: 508 [M+Na], 993 [2M+Na].

To a solution of the crude Compound 3 (57.7 g, 119 mmol) in anhydrous DCM (1 L) was added AcOH (78.4 g, 1.3 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (11.3 g, 0.3 mol) was added in small portions over 1 hour. After stirring for a another 1 hour at −5° C., saturated aqueous NaCl (300 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over anhydrous MgSO₄, filtered and concentrated to yield the crude product, which was further purified by chromatography (hexanes:EtOAc=6:1) to yield Compound 4 (28 g, light yellow oil). LC-MS: 494 [M+Na], 965 [2M+Na].

To a solution of Compound 4 (28 g, 60 mmol) in anhydrous DMF (250 mL) was added K₂CO₃ (9.9 g, 72 mmol) and CH₃I (25.6 g, 180 mmol) at 0° C. under nitrogen. After stirring for 1 hour at 0° C., the mixture was warmed to room temperature and stirred overnight. The mixture was diluted with water (3 L) and extracted with EtOAc (3×300 mL). The combined organic layers were washed with saturated aqueous NaCl (500 mL), dried over anhydrous Na₂SO₄, and concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=5:1) to yield the title compound (11.7 g, light yellow solid). LC-MS: 508 [M+Na], 993 [2M+Na]. ¹H NMR (300 MHz, CD₃OD): δ7.52-7.49 (m, 2H), 7.41-7.39 (m, 2H), 7.32-7.27 (m, 3H), 7.07-7.01 (m, 1H), 6.21-6.18 (d, 1H), 3.79 (m, 1H), 2.78-2.61 (m, 2H), 2.35-2.20 (m, 2H), 1.76 (s, 6H), 1.59 (s, 3H), 2.21 (s, 1H), 1.28 (s, 9H).

Preparation 28 (2S,4R)-4-t-Butoxycarbonylamino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methylpentanoic Acid (P²=BOC) and (2S,4R)-4-Amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methylpentanoic Acid (P² removed)

Distilled Water (181 mL) was purged 1 hour under nitrogen, then cannulated into a vessel containing 0.1 M of samarium diiodide in THF (800 mL). While maintaining an atmosphere of nitrogen, a similarly degassed solution of [(R)-1-(3′-fluorobiphenyl-4-ylmethyl)-2-(2,2,5-trimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-ethyl]-carbamic acid t-butyl ester (4.9 g, 10.0 mmol) and THF (20 mL) was added via canula. The resulting mixture was stirred for 15 minutes, then exposed to air. The solvent was evaporated, and EtOAc (200 mL), saturated aqueous NaCl (50 mL) and 10% citric acid (20 mL) were added. The mixture was stirred for 5 minutes, then both layers were extracted. The organic layer was dried over Na₂SO₄ and concentrated under vacuum. The crude product was purified by chromatography (330 g gold column, 1:1 ether:EtOAc with 0.5% AcOH) to yield the BOC-protected acid. (P²=BOC) (1.5 g). A portion of the BOC-protected acid was dissolved in 4M HCl in dioxane (6 mL) and MeCN (10 mL). The solvent was evaporated under vacuum to yield the acid (P² removed).

Preparation 29 3-(N-Biphenyl-4-ylmethyl-N′-t-butoxycarbonylhydrazino)-2-hydroxy-2-methylpropionic Acid Methyl Ester

4-(Bromomethyl)biphenyl (2.00 g, 8.09 mmol) and DIPEA (1.4 mL, 8.1 mmol) were dissolved in DMF (40.0 mL), then t-butyl carbazate (2.1 g, 16.2 mmol) was added and the mixture was stirred at room temperature overnight. Upon completion of the reaction, the mixture was partially concentrated, and the residue was partitioned between EtOAc and saturated aqueous NaHCO₃. The EtOAc layer was dried over Na₂SO₄ and concentrated. The crude product was purified by flash chromatography (0-60% EtOAc/hexanes with 0.5% DIPEA) to yield Compound 1 (1.3 g.)

Compound 1 (460 mg, 1.5 mmol) was dissolved in isopropyl alcohol (10.0 mL), then methyl 2-methylglycidate (180 μL, 1.7 mmol) was added and the mixture was heated to 85° C. overnight. Upon completion of the reaction, the mixture was partitioned between EtOAc and saturated aqueous NaHCO₃. The EtOAc layer was then dried over Na₂SO₄ and concentrated to yield the title compound (0.5 g), which was used without further purification.

Preparation 30 (R)-3-[N-(4-Bromobenzyl)-N′-t-butoxycarbonylhydrazino]-2-hydroxypropionic Acid Methyl Ester

4-Bromobenzyl bromide (5.0 g, 20 mmol) and DIPEA (3.48 mL, 20.0 mmol) were dissolved in DMF (20 mL). t-Butyl carbazate (7.9 g, 60.0 mmol) was added and the mixture was stirred at room temperature until the reaction was complete. The mixture was partially concentrated, then the residue was partitioned between EtOAc and saturated aqueous NaHCO₃. The EtOAc layer was then dried over Na₂SO₄ and concentrated. The crude product was purified by flash chromatography to yield Compound 1 (3.8 g).

Compound 1 (1.9 g, 6.3 mmol) was dissolved in isopropyl alcohol (26.4 mL). Methyl (2R)-glycidate (1.1 mL, 12.6 mmol) was added and the mixture was heated at 90° C. until the reaction was complete (˜4 days). The mixture was cooled to room temperature and concentrated to yield the title compound (2.5 g) as a white solid.

Preparation 31 (R)-3-[N-(3′-Chlorobiphenyl-4-ylmethyl)hydrazino]-2-hydr-2-oxypropionic Acid Ethyl Ester

(R)-3-[N-(4-Bromobenzyl)-N′-t-butoxycarbonylhydrazino]-2-hydroxypropionic acid methyl ester (600 mg, 1 mmol), 3-chlorophenylboronic acid (419 mg, 2.7 mmol), and K₂CO₃ (617 mg, 4.5 mmol) were combined in EtOH (5 mL) and water (1 mL), followed by the addition of SilicaCat® Pd(0) (0.09 mmol/g loading, 1160 mg, 104 μmol). The mixture was heated in a microwave reactor at 120° C. until the reaction was complete (˜30 minutes). The mixture was filtered and concentrated. The residue was dissolved into MeCN/AcOH and purified by reverse phase chromatography (55 g column; gradient 30-95% MeCN in water with 0.1% TFA). The clean fractions were collected, concentrated and then dissolved in 4M HCl in dioxane (6 mL) and EtOH (6 mL). The mixture was stirred at room temperature overnight, then concentrated to yield the title compound (250 mg), which was used without further purification.

Preparation 32 (S)-2-(1-Biphenyl-4-yl-1-methylethyl)-5-oxo-pyrrolidine-1-carboxylic Acid t-Butyl Ester

To a solution of 2-(4-bromophenyl)acetonitrile (130.0 g, 0.7 mol) and iodomethane (103.9 mL, 1.7 mol) in THF (1.0 L) was added NaH (60% dispersion in mineral oil, 66.7 g, 1.7 mol) in small portions at 10° C. After completion of the addition, the mixture was stirred at 10° C. for another 2 hours. The mixture was poured into ice water (2.0 L) and extracted with EtOAc (1.5 L). The organic layer was washed with saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 1 (175 g, containing mineral oil) as a yellow oil, which was used directly without further purification. ¹H NMR (CDCl₃, 300 MHz) δ 7.52 (d, J=9.0 Hz, 2H), 7.38 (d, J=9.0 Hz, 2H), 1.72 (s, 6H).

To a solution of Compound 1 (175 g, containing mineral oil) in DCM (1.0 L) was added DIBAL (1.0 M solution in DCM, 700 mL, 0.70 mol) dropwise at −78° C. The reaction mixture was stirred at −78° C. for 1.5 hours and then quenched carefully with 3.0 N HCl (1.0 L). The resulting mixture was stirred at room temperature overnight and the organic layer was washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄ and concentrated to yield Compound 2 (180 g) as a yellow oil, which was used directly without further purification. ¹H NMR (CDCl₃, 300 MHz) δ 9.48 (s, 1H), 7.53 (d, J=11.0 Hz, 2H), 7.17 (d, J=11.0 Hz, 2H), 1.46 (s, 6H).

To an aqueous solution of NaCN (32.7 g in 1.0 L of H₂O, 0.7 mol) were added (NH₄)₂CO₃ (380 g, 4.0 mol) and Compound 2 (180 g). The reaction mixture was refluxed overnight and then concentrated under reduced pressure at 75° C. Water (350 mL) was added to the residue and the mixture was concentrated again. The residue was suspended in petroleum ether (700 mL) and water (250 mL) and the resulting mixture was stirred at room temperature for 15 minutes. The precipitate was collected by filtration and dried to yield Compound 3 (150 g) as a white solid. ¹H NMR (DMSO-d6, 300 MHz) δ 10.39 (s, 1H), 8.05 (s, 1H), 7.48 (d, J=9.0 Hz, 2H), 7.28 (d, J=9.0 Hz, 2H), 4.17 (s, 1H), 1.42 (s, 3H), 1.34 (s, 3H).

A suspension of Compound 3 (150 g, 0.51 mol) in 6.0 N NaOH (400 mL) and ethane-1,2-diol (300 mL) was stirred at 120° C. for 38 hours. The mixture was cooled to room temperature and neutralized with an HCl solution. The precipitate was collected by filtration and dried to yield Compound 4 (250 g, containing NaCl salt) as a white solid. ¹H NMR (DMSO-d6, 300 MHz) δ 7.35 (d, J=9.0 Hz, 2H), 7.17 (d, J=9.0 Hz, 2H), 3.22 (s, 1H), 1.16 (s, 3H), 1.15 (s, 3H).

To a suspension of Compound 4 (250 g, containing NaCl salt) in MeOH (1.0 L) was added thionyl chloride (72.0 mL, 1.0 mol) dropwise at 5° C. The mixture was refluxed overnight and the solvent was removed under reduced pressure. The residue was partitioned between DCM (1.0 L) and saturated aqueous NaHCO₃ (1.5 L). The organic layer was washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄ and concentrated to yield the corresponding methyl ester (90.0 g). 2-Phenylacetyl chloride (48.6 g, 0.32 mol) was added dropwise to a solution of the ester (90.0 g) and Et₃N (56.5 mL, 0.41 mol) in DCM (1.0 L) at 0° C. and the mixture was stirred at 0° C. for 30 minutes. The mixture was washed with 1.0 N HCl (500 mL) and saturated aqueous NaCl, respectively. The organic layer was dried over anhydrous Na₂SO₄ and concentrated to yield Compound 5 (120 g). ¹H NMR (CDCl₃, 300 MHz) δ 7.32 (m, 5H), 7.18 (m, 2H), 6.95 (m, 2H), 5.68 (br s, 1H), 4.76 (d, J=9.0 Hz, 1H), 3.57 (s, 3H), 3.53 (d, J=5.0 Hz, 2H), 1.30 (s, 3H), 1.25 (s, 3H).

To a solution of Compound 5 (120 g, 0.30 mol) in MeOH (500 mL) was added 4.0 N NaOH (200 mL). The mixture was stirred at room temperature for 4 hours and then the pH was adjusted to pH=1 with 3.0 N HCl. The resulting mixture was extracted with EtOAc (2×300 mL). The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄, and concentrated under reduced pressure. The residue was recrystallized from EtOAc/hexanes to yield Compound 6 (82.0 g). ¹H NMR (DMSO-d6, 300 MHz) δ 7.41 (d, J=6.0 Hz, 2H), 7.22 (m, 5H), 6.99 (d, J=6.0 Hz, 2H), 4.65 (d, J=9.0 Hz, 1H), 3.52 (d, J=14.0 Hz, 1H), 3.36 (d, J=14.0 Hz, 1H), 1.34 (s, 3H), 1.30 (s, 3H).

A suspension of Compound 6 (82.0 g, 0.21 mol) in distilled water (3.0 L) was adjusted to pH=8.5 with 3.0 N LiOH and a clear solution was formed. Immobilized Penicillinase (20.0 g) was added and the resulting mixture was stirred at 37° C. for 60 hours. The mixture was filtered and the filtrate was adjusted to pH=1 with 3.0 N HCl and extracted with EtOAc. The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄ and concentrated to yield Compound 7 (59.0 g, 80% ee, containing 2-phenylacetic acid).

A suspension of Compound 7 (59.0 g, containing 2-phenylacetic acid) in 6.0 N HCl (500 mL) was refluxed overnight. The mixture was washed with EtOAc (300 mL) and the aqueous phase was concentrated under reduced pressure to yield the corresponding amino acid as its hydrochloride salt. The salt was dissolved in water (300 mL) and the solution was adjusted to pH=1. A solution of (BOC)₂O (33.0 g, 0.2 mol) in acetone (200 mL) was added and the mixture was stirred at room temperature for 2 hours. The mixture was washed with hexanes (200 mL) and the aqueous phase was adjusted to pH=2. The resulting mixture was extracted with EtOAc (2×300 mL). The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄ and concentrated to yield Compound 8 (37.0 g) as a white solid. ¹H NMR (CDCl₃, 300 MHz) δ 9.48 (br s, 1H), 7.46 (d, J=7.0 Hz, 2H), 7.26 (d, J=7.0 Hz, 2H), 5.02 (br s, 1H), 4.56 (d, J=9.0 Hz, 1H), 1.39 (s, 9H).

A mixture of Compound 8 (37.0 g, 0.1 mol) in dioxane (200 mL) and 1.0 N K₂CO₃ (200 mL) was degassed for 30 minutes with nitrogen, followed by the addition of phenylboronic acid (13.4 g, 0.1 mol) and Pd(PPh₃)₄ (1.6 g, 1.4 mmol). The mixture was heated at 75° C. for 8 hours and then cooled to room temperature. The mixture was washed with EtOAc/hexanes (150 mL, 1:1) and the aqueous phase was adjusted to pH=2 and extracted with EtOAc (2×300 mL). The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous Na₂SO₄ and concentrated to yield Compound 9 (31.0 g, 84% yield) as a white solid.

A solution of Compound 9 (31.0 g, 84 mmol), Meldrum's acid (13.3 g, 92 mmol) and DMAP (15.4 g, 0.13 mol) in DCM (400 mL) was cooled to −5° C. and a solution of DCC (19.0 g, 92 mmol) in DCM (200 mL) was added over 1 hour. The mixture was stirred at −5° C. overnight. The precipitate was filtered off and the filtrate was washed with 1.0 N HCl (2×700 mL) and saturated aqueous NaCl, respectively. After the organic layer containing Compound 10 was dried over anhydrous MgSO₄, it was used directly for the next step without concentration.

A solution of Compound 10 in DCM (600 mL) was cooled to −5° C. and AcOH (45.0 mL) was added. Then NaBH₄ (7.0 g, 0.2 mol) was added in small portions over 30 minutes and the mixture was stirred at −5° C. for 3 hours. Water (50.0 mL) was added dropwise followed by addition of saturated aqueous NaCl (450 mL). The organic layer was washed with water (2×300 mL) and saturated aqueous NaHCO₃ (2×300 mL), dried over anhydrous MgSO₄ and concentrated to yield Compound 11 (32.0 g, 75% ee) as an off-white solid. After recrystallization from EtOH, chirally pure Compound 11 (13.0 g) was obtained. ¹H NMR (CDCl₃, 300 MHz) δ 7.61 (m, 10H), 4.46 (br s, 1H), 4.26 (m, 1H), 3.72 (br s, 1H), 2.23 (m, 1H), 1.79 (s, 3H), 1.76 (s, 3H), 1.48 (s, 6H), 1.39 (s, 9H).

A solution of Compound 11 (13.0 g, 27.0 mmol) in toluene (100.0 mL) was refluxed for 3 hours. After evaporation of the solvent, the residue was recrystallized from hexanes/EtOAc (3:1) to yield the title compound (8.0 g) as a white solid.

Preparation 33 (2R,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxy-5-methylhexanoic Acid Ethyl Ester

A mixture of (S)-2-(1-biphenyl-4-yl-1-methylethyl)-5-oxo-pyrrolidine-1-carboxylic acid t-butyl ester (14.0 g, 36.9 mmol, racemic) in a 3.0 N HCl-EtOAc solution (150 mL) was stirred at room temperature for 3 hours. The solvent was removed under reduced pressure to yield Compound 1 (10.0 g) as a white solid.

To a solution of Compound 1 (10.0 g, 35.8 mmol) in THF (80.0 mL) was added BuLi (2.5 M in hexanes, 15.0 mL) dropwise at −78° C. After the mixture was stirred for 30 minutes pivaloyl chloride (4.8 mL, 39.4 mmol) was added dropwise. The mixture was stirred at −78° C. for 1 hour and then quenched with saturated aqueous NH₄Cl. The resulting mixture was extracted with EtOAc and the combined extracts were washed with saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated. The residue was purified by flash column chromatography on silica gel to yield Compound 2 (9.0 g) as a white solid.

To a solution of Compound 2 (9.0 g, 24.7 mmol) in THF (50.0 mL) was added sodium bis(trimethylsilyl)amide (2.0 M in THF, 18.5 mL, 37.0 mmol) dropwise at −78° C. The mixture was stirred for 20 minutes and a solution of oxaziridine derivative (10.8 g, 37.0 mmol) in THF (30.0 mL) was added dropwise. The mixture was stirred at −78° C. for 30 minutes and then quenched with saturated aqueous NH₄Cl. The resulting mixture was extracted with EtOAc (1.0 L) and the extract was washed with 1.0 N HCl and saturated aqueous NaCl, dried over anhydrous MgSO₄ and evaporated to remove most of the solvent. The precipitate was filtered off and the filtrate was concentrated. The residue was purified by flash column chromatography on silica gel (DCM:hexanes=1:1 to DCM) to yield Compound 3 (4.3 g, racemic). This racemate was subjected to chiral AD-column chromatography to afford chirally pure Compound 3 (1.4 g). ¹H NMR (DMSO-d6, 300 MHz) δ 7.63 (m, 4H), 7.49 (m, 4H), 4.83 (d, 1H), 3.29 (m, 1H), 2.31 (m, 2H), 1.40 (s, 3H), 1.36 (s, 3H), 1.28 (s, 9H). LC-MS (ESI): m/z 380.1 [M+H]+.

A solution of Compound 3 (1.7 g, 160 mmol) in EtOH (15.0 mL) and 12.0 N HCl (15.0 mL) was heated at 90-95° C. for 20 hours. The solvent was removed and the residue was treated with a 3.0 N HCl-EtOH solution (25.0 mL) under reflux for another 3 hours. After removal of the solvent, the residue was purified by preparative HPLC to yield the title compound (0.6 g) as a foamy solid HCl salt. ¹H NMR (DMSO-d6, 300 MHz) δ 7.88 (br s, 3H), 7.68 (m, 4H), 7.49 (m, 4H), 7.35 (m, 1H), 6.11 (br s, 1H), 4.11 (br s, 1H), 4.05 (q, 2H), 3.61 (br s, 1H), 1.67 (m, 2H), 1.40 (s, 3H), 1.36 (s, 3H), 1.09 (t, 3H). LC-MS (ESI): m/z 342.1 [M+H]+.

Preparation 34 (2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-5-methylhexanoic Acid Ethyl Ester

A mixture of (S)-2-(1-biphenyl-4-yl-1-methylethyl)-5-oxo-pyrrolidine-1-carboxylic acid t-butyl ester (8.0 g, 21.2 mmol) and t-butoxy-N,N,N′,N′-tetramethylmethanediamine (10.0 g, 63.6 mmol) was heated at 80° C. for 3 hours. The mixture was cooled to room temperature and diluted with EtOAc (200 mL). The resulting solution was washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 1 (9.2 g, quantitative) as an oil. ¹H NMR (CDCl₃, 300 MHz) δ 7.53 (m, 9H), 6.95 (s, 1H), 4.60 (br s, 1H), 2.90 (s, 1H), 2.62 (m, 2H), 1.61 (s, 9H), 1.39 (s, 3H), 1.34 (s, 3H).

To a solution of Compound 1 (9.2 g, 21.2 mmol) in THF (80.0 mL) was added 1.0 N HCl (25.0 mL) at 0° C. The mixture was stirred at room temperature for 2 hours and then diluted with EtOAc (100 mL). The resulting mixture was neutralized with saturated aqueous NaHCO₃ and extracted with EtOAc (2×100 mL). The combined extracts were washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 2 (8.6 g, quantitative) as an oil. LC-MS (ESI): m/z 430.1 [M+Na]+.

To a solution of Compound 2 (8.6 g, 21.2 mmol) in THF (150 mL) and EtOH (15.0 mL) was added AcOH (24.3 mL, 0.4 mol) at −5° C. After the mixture was stirred at −5° C. for 30 minutes, NaBH₃CN (5.3 g, 84.8 mmol) was added in small portions over 1 hour. The mixture was stirred at −5° C. for 1 hour and neutralized with saturated aqueous NaHCO₃. The resulting mixture was extracted with EtOAc (2×100 mL). The combined extracts were washed with water (2×100 mL) and saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated to yield Compound 3 (8.67 g, quantitative) as a foamy solid.

To a solution of Compound 3 (3.5 g, 8.6 mmol) in EtOH (30.0 mL) was added K₂CO₃ (2.4 g, 17.1 mmol) at 0° C. The mixture was stirred at 0° C. for 1 hour and then allowed to warm to room temperature and stirred overnight. The mixture was filtered and the filtrate was concentrated. The residue was treated with water (20 mL) and the resulting mixture was extracted with DCM (3×25 mL). The combined extracts were washed with saturated aqueous NaCl, dried over anhydrous MgSO₄ and concentrated. The residue was purified by flash column chromatography on silica gel (hexanes:EtOAc=6:1) to yield Compound 4 (2.2 g) as a foamy solid. ¹H NMR (CDCl₃, 300 MHz) δ 7.53 (m, 9H), 4.35 (br s, 1H), 4.15 (m, 2H), 3.95 (br s, 1H), 3.65 (m, 2H), 2.61 (br s, 1H), 1.79 (m, 1H), 1.45 (s, 9H), 1.35 (s, 3H), 1.29 (s, 3H), 1.25 (t, 3H). LC-MS (ESI): m/z 478.2 [M+Na]+.

A mixture of Compound 4 (2.2 g, 4.8 mmol) in a 2.0 N HCl-EtOH solution (30.0 mL) was stirred at room temperature for 3 hours. Removal of the solvent under reduced pressure yielded the title compound (1.6 g) as a foamy solid HCl salt. ¹H NMR (DMSO-d6, 300 MHz) δ 8.08 (br s, 3H), 7.55 (m, 9H), 4.95 (br s, 1H), 3.95 (m, 2H), 3.48 (m, 2H), 2.75 (br s, 1H), 1.79 (m, 2H), 1.47 (s, 3H), 1.40 (s, 3H), 1.09 (t, 3H). LC-MS (ESI): m/z 356.1 [M+H]+.

Preparation 35 3-[N-(4-Bromobenzyl)hydrazino]-2-hydroxypropionic Acid Ethyl Ester

A solution of (R)-3-[N-(4-bromobenzyl)-N′-t-butoxycarbonylhydrazino]-2-hydroxypropionic acid methyl ester (25 g, 62 mmol) in EtOH/HCl (310 mL, 1.0 M, 0.3 mol) was stirred overnight. The mixture was concentrated and the reside was washed with EtOAc (120 mL) and filtered to yield the title compound as a white solid HCl salt (15 g).

Preparation 36 Oxalic acid (R)-2-[N-(4-bromobenzyl)-N′-ethoxyoxalylhydrazino]-1-ethoxycarbonylethyl Ester Ethyl Ester

Ethyl oxalyl chloride (70 μL, 630 μmol) was added dropwise to a solution of 3-[N-(4-bromobenzyl)hydrazino]-2-hydroxypropionic acid ethyl ester (200 mg, 630 μmol) and Et₃N (220 μL, 1.6 mmol) in DCM (4.0 mL, 62.2 mmol) at 0° C. The resulting mixture was stirred for 15 minutes at 0° C. and for 15 minutes at room temperature. Water (3 mL) was added, the layers were separated, and the aqueous layer was extracted with DCM (2×2 mL). The DCM layers were combined, dried over MgSO₄, and concentrated to yield the title compound (275 mg).

Preparation 37 N′-(4-Bromobenzyl)hydrazinecarboxylic Acid t-Butyl Ester

To a stirred solution of t-butyl carbazate (50 g, 0.4 mol) in dry THF (400 mL) was added dropwise a solution of 4-bromobenzaldehyde (70 g, 0.4 mol) in dry THF (200 mL). The mixture was stirred at room temperature for 2 hours, and then concentrated in vacuo to yield Compound 1 as a yellow solid (113.8 g). LC-MS: 243 [M-tBu+H]⁺.

To a solution of Compound 1 (113.8 g, 0.4 mol) in dry THF (1 L) was added NaCNBH₃ (36 g, 0.6 mol) in portions at 0° C. AcOH (180 mL) was added dropwise and the resulting mixture was stirred at room temperature overnight. Water (2 L) and EtOAc (1.5 L) were added and the aqueous phase was adjusted to pH=7 with a saturated aqueous Na₂CO₃ solution. The organic layer was separated, washed with saturated aqueous NaCl and water (200 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo. The residue was treated with MeOH (2 L) and IN NaOH (1.5 L), and then stirred at room temperature for 2 hours. After the removal of the MeOH solvent, the precipitate was collected by filtration to yield the title compound as a white solid (112 g). LC-MS: 245 [M-tBu+H]⁺.

Preparation 38 (R)-3-[N′-t-Butoxycarbonyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic Acid Methyl Ester

To a solution of N′-(4-bromobenzyl)hydrazinecarboxylic acid t-butyl ester (60 g, 0.2 mol) in 1,4-dioxane (1.5 mL) was added 5-chloro-2-fluorophenylboronic acid (38 g, 0.2 mol) and Pd(dppf)Cl₂ (7.3 g). The mixture was stirred at room temperature under nitrogen for 10 minutes, and then, K₂CO₃ (55.2 g, 0.4 mol) in water (240 mL) was added. The resulting mixture was stirred at 60° C. for 3 hours, and then cooled to room temperature and concentrated in vacuo. The residue was extracted with EtOAc (3×300 mL). The combined organic layers were dried over anhydrous Na₂SO₄ and concentrated in vacuo. The product was purified by column chromatography (PE:EtOAc=10: 1-5:1) to yield Compound 1 as a pink solid (56 g). LC-MS: 701 [2M+H]⁺

To a solution of Compound 1 (20 g, 57 mmol) in isopropyl alcohol (250 mL) was added methyl (2R)-glycidate (8.7 g, 86 mmol) under nitrogen. The mixture was stirred at 85° C. for 3 days, then cooled to room temperature. The precipitated solid was collected by filtration to yield the title compound as an off-white solid (18.5 g). LC-MS: 397 [M-tBu+H]⁺.

Preparation 39 (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic Acid Ethyl Ester

A solution of (R)-3-[N′-t-butoxycarbonyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid methyl ester (20 g, 16 mmol) in HCl/EtOH (1.1 M, 200 mL) was stirred overnight and then concentrated in vacuo. The residue was dispersed in EtOAc (2×40 mL), and the precipitate was collected by filtration to give the title compound as an off-white solid HCl salt (8.8 g). LC-MS: 367 [M+H]⁺. ¹H NMR (300 MHz, DMSO-d₆) δ 1.05 (t, J=7.2 Hz, 3H), 3.05-3.03 (q, J=7.2 Hz, 2H), 4.06-3.95 (m, 4H), 4.42 (br, 1H), 6.46 (br, 1H), 7.62-7.40 (m, 7H), 9.42 (s, 3H).

Preparation 40 (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl Ester

3-[N-(4-Bromobenzyl)hydrazino]-2-hydroxypropionic acid ethyl ester (3.1 g, 9.6 mmol) was combined with di-t-butyldicarbonate (4.2 g, 19.2 mmol) and DCM (92.4 mL, 1.4 mol). DIPEA (5.0 mL, 28.8 mmol) was added and the resulting mixture was stirred at room temperature for 24 hours. The mixture was concentrated and the reside was dissolved into DCM and purified by flash chromatography (10-95% EtOAc in hexanes). The clean fractions were collected and concentrated to yield Compound 1 as a white powder (4.0 g).

Compound 1 (3.5 g, 8.4 mmol) was combined with 5-chloro-2-fluorophenylboronic acid (1.8 g, 10.1 mmol) and K₂CO₃ (3.5 g, 25.2 mmol) in EtOH (29.4 mL, 503 mmol) and water (7.6 mL, 419 mmol). The resulting mixture was placed under nitrogen and SilicaCat DPP-Pd (0.28 mmol/g loading; 3.0 g, 839 μmol) was then added. The mixture was microwaved at 120° C. for 15 minutes. The mixture was then filtered and evaporated under reduced pressure. The crude residue was purified using flash chromatography (10-90% EtOAc in hexanes) to yield Compound 2 (2.0 g).

Compound 2 (500 mg, 1 mmol) was combined with K₂CO₃ (315 mg, 2.3 mmol) in DMF (5.3 mL, 68.4 mmol). 2-Bromoacetophenone (249 mg, 1.3 mmol) was then added and the resulting mixture was stirred at room temperature for 15 minutes. The mixture was then purified using flash chromatography (50-100% EtOAc in Hexanes). This purified material (605 mg) was then dissolved in MeCN (3.6 mL, 68.4 mmol). A solution of 4 M HCl in 1,4-dioxane (1.4 mL, 5.7 mmol) was then added, and the resulting mixture was stirred for 1 hour to yield the title compound (245 mg).

Preparation 41 (R)-3-[N′-t-Butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic Acid

t-Butyl oxalyl chloride was prepared by adding oxalyl chloride (102 μL, 1.2 mmol) to a solution of t-butyl alcohol (35 μL, 361 μmol) in ether (632 μL, 6.0 mmol). The resulting mixture was stirred at room temperature for 15 minutes and then concentrated in vacuo to yield a clear colorless liquid.

(R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (55.0 mg, 120 μmol) was dissolved in DCM (463 μL, 7.2 mmol). The t-butyl oxalyl chloride was added, and the resulting mixture was stirred at room temperature for 30 minutes, and then concentrated in vacuo. The resulting residue was dissolved in AcOH (411 μL, 7.2 mmol). Zinc (394 mg, 6.0 mmol) was added to the mixture, which was then stirred at room temperature for 10 minutes. The mixture was filtrated and purified (Interchim reverse phase column) to yield the title compound (25.0 mg).

Preparation 42 (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic Acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl Ester

LiOH hydrate (3 g, 73 mmol) in water (60 mL) was added to (R)-3-[N′-t-butoxycarbonyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid methyl ester (16.5 g, 36.5 mmol) in MeOH (300 mL). The mixture was stirred at room temperature for 2 hours, and the MeOH was evaporated in vacuo. The mixture was adjusted to pH=5 with 1 M aqueous HCl, and the residue was extracted with EtOAc (2×300 mL). The combined organic layers were dried over anhydrous Na₂SO₄, and concentrated in vacuo to yield Compound 1 as a white solid (18 g). LC-MS: 383 [M-tBu+H].

To a solution of Compound 1 (1.5 g, 3.42 mmol), K₂CO₃ (0.95 g, 6.84 mmol) and potassium iodide (20 mg) in DMF (40 mL) was added 4-(bromomethyl)-5-methyl-1,3-dioxol-2-one (0.8 g, 4.1 mmol) in DMF (15 mL). The resulting mixture was stirred for 4 hours at room temperature. Saturated aqueous NaCl (30 mL) was added and the mixture was extracted with EtOAc (2×50 mL). The combined organic layers were dried over anhydrous Na₂SO₄ and concentrated in vacuo. The residue was purified by column chromatography (hexanes/EtOAc=1:1) to yield Compound 2 as a yellow solid (930 mg).

LC-MS: 495 [M-tBu+H]⁺.

Compound 2 (400 mg, 0.73 mmol) was dissolved in MeCN (20 mL), and cooled to 0° C. N-trimethylsilylimidazole (290 mg, 1.46 mmol) was added dropwise and the resulting mixture was stirred for 2 hours. MeOH (50 mL) was added to quench the reaction. The mixture was washed with saturated aqueous NaCl (2×50 mL) and extracted with DCM (2×80 mL). The combined organic layers were dried over anhydrous Na₂SO₄ and concentrated in vacuo. The product was collected to yield the title compound as a yellow solid (200 mg). LC-MS: 451 [M+H]⁺.

Preparation 43 (R)-3-[N′-t-Butoxoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-methyl)-hydrazino]-2-hydroxypropionic Acid

To a mixture of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (2.0 g, 4.4 mmol) in DCM (10 mL) was added dropwise t-butyl 2-chloro-2-oxoacetate (1.5 g, 8.8 mmol) at 0° C. under nitrogen. DIPEA (1.15 g, 8.8 mmol) was then added dropwise, and the resulting mixture was stirred for 5 minutes at 0° C. The solvent was removed by evaporation and the residue was purified by column chromatography (PE:EtOAc=2:1) to yield Compound 1 as a yellow liquid (2.0 g). LC-MS: 585[M+H]⁺.

A mixture of Compound 1 (2.0 g, 3.4 mmol) and Zn (15.5 g, 240 mmol) in AcOH (15 mL) was stirred for 1 hour at room temperature, then filtered. Water (30 mL) was added to the filtrate, and the mixture was extracted with EtOAc (3×40 mL). The combined organic layers were washed with saturated aqueous NaCl (2×50 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo. The residue was purified by column chromatography (DCM/MeOH=10:1) to yield the title compound as a yellow liquid (1.4 g). LC-MS: 467 [M+H]⁺.

Example 1 (R)-5-Biphenyl-4-yl-2-hydroxy-4-(oxalylamino)pentanoic Acid

(R)-4-Amino-5-biphenyl-4-yl-2-hydroxypentanoic acid ethyl ester (HCl salt; 47 mg, 0.2 mmol) and ethyl oxalyl chloride (18.4 μL, 1.1 eq) were combined with DIPEA (52.2 μL, 0.3 mmol) in DMF (0.3 mL)/DCM (0.3 mL). The mixture was stirred at room temperature until the reaction was complete. The solvent was removed and the residue was dissolved in EtOH (750 μL) and 1 M aqueous NaOH (750 μL), and stirred at room temperature overnight. The solvent was removed and the residue was purified by preparative HPLC to yield the title compound (28.2 mg, purity 100%). MS m/z [M+H]⁺ calc'd for C₁₉H₁₉NO₆, 358.12. found 358.0.

Example 2 A. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid

A solution of ethyl oxalyl chloride (70.7 μL, 0.6 mmol) in DIPEA (165 μL, 0.9 mmol) was added to a solution of (2R,4R)-4-amino-5-(4-bromophenyl)-2-hydroxypentanoic acid ethyl ester (100 mg, 0.3 mmol) and DCM (0.7 mL), and the resulting mixture was stirred at room temperature for 10 minutes, followed by evaporation of the solvent under reduced pressure. 3-Chlorophenylboronic acid, pinacol ester (112 mg, 468 μmol), K₂CO₃ (97 mg, 702 μmol), EtOH (2 mL), and water (0.6 mL) were added, followed by the addition of SilicaCat® Pd(0) (0.09 mmol/g loading, 260 mg, 23.4 μmol). The mixture was heated at 120° C. for 20 minutes. The reaction mixture was concentrated and 10 M of aqueous NaOH (316 μL) and THF (4.0 mL) with 1 drop of MeOH was added. The resulting mixture was stirred at room temperature for 1 hour. The residue was dissolved in AcOH and purified by preparative HPLC to yield the title compound (9 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₁₉H₁₈ClNO₆, 392.08. found 392.4.

B. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Ethyl Ester

Oxalyl chloride (54.5 μL, 0.6 mmol) was added to a solution of t-butyl alcohol (56.0 μL) in ether (1.0 mL) and the mixture was stirred for 1 hour at room temperature. The mixture was concentrated under vacuum and a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (67.9 mg, 0.2 mmol) and DIPEA (102 μL, 0.6 mmol,) in DCM (1.0 mL) was added to the resulting clear colorless liquid residue. The resulting mixture was stirred at room temperature for 2 hours and concentrated under vacuum to yield a clear yellow liquid. A 1:1 TFA/DCM (1.6 mL) was added to the crude liquid and the reaction mixture was stirred at room temperature for 2 hours and concentrated under vacuum to yield a clear yellow liquid. The crude liquid was purified by reverse phase preparative HPLC (40-90% MeCN/H₂O) to yield the title compound (25.0 mg, purity 95%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₁H₂₂ClNO₆, 420.11. found 420.1.

C. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxypentanoic Acid Ethyl Ester

A solution of ethyl oxalyl chloride (24.6 μL, 0.2 mmol) in DCM (0.4 mL) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (69.6 mg, 0.2 mmol) and Et₃N (69.7 μL, 0.5 mmol) in DCM (1.0 mL) at 0° C. over a period of 10 minutes. The resulting mixture was stirred at 0° C. for 30 minutes, and then for 15 minutes at room temperature. Water (2 mL) was added, the layers were separated, and the aqueous layer was extracted with DCM (2×2 mL). The DCM layers were combined, dried over Na₂SO₄, and concentrated to yield a clear yellow liquid. The crude liquid was purified by flash chromatography (4 g column, 16 mL/min, using 35% EtOAc/hexanes (2 min), 35-50% (1 min), 50% (4 min), 50-70% (1 min) and 70% EtOAc/hexanes (3 min)) to yield the title compound (63.9 mg, purity 90%) as a clear colorless liquid which solidified upon standing to a white solid. MS m/z [M+H]⁺ calc'd for C₂₃H₂₆ClNO₆, 448.14. found 448.2.

D. (2R,4R)-4-(Butoxyoxalylamino)-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic Acid Butyl Ester

p-Toluenesulfonic acid monohydrate (849 μg, 4 μmol) was added to a solution of (2R,4R)-5-(3′-chlorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxypentanoic acid ethyl ester (20.0 mg, 45 μmol) in 1-butanol (0.5 mL). The reaction mixture was stirred at 80° C. for 14 hours, at 90° C. for 4 hours, and then was allowed to cool to room temperature. Saturated aqueous NaHCO₃ (2 mL) was added, and the aqueous layer was extracted with DCM (3×2 mL). The DCM layers were combined, dried over Na₂SO₄, and concentrated under vacuum to yield a clear colorless liquid. The crude liquid was purified by flash chromatography (4 g column, 40% EtOAc/hexanes) to yield the title compound (18.1 mg, purity 99%) as a clear colorless liquid. MS m/z [M+H]⁺ calc'd for C₂₇H₃₄ClNO₆, 504.21. found 504.2.

E. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-[(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxyoxalyl)amino]pentanoic Acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl Ester

Oxalyl chloride (22.4 μL, 264 μmol) was added to a solution of 4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one (29.1 mg, 224 μmol) in ether (1.5 mL) and the mixture was stirred at room temperature for 2 hours. The ether was removed under vacuum and the residue was dissolved in DMF (1.5 mL). The resulting solution was added to a solution of (2R,4R)-4-amino-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic acid (65.0 mg, 203 μmol) and NaHCO₃ (51.2 mg) at 0° C. The resulting mixture was stirred at room temperature for 3 hours, then concentrated under vacuum. The residue was then purified by reverse phase preparative HPLC (30%-90% MeCN/H₂O) to yield compound 1 (19.1 mg) as a white solid.

1-Hydroxybenzotriazole (7.7 mg, 56.8 μmol) and N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (10.9 mg, 56.8 μmol) were added to a solution of compound 1 (19.1 mg, 37.9 μmol) in DCM (1.0 mL) and the mixture was stirred at room temperature for 10 minutes. 4-Hydroxymethyl-5-methyl-[1,3]dioxol-2-one (14.8 mg, 114 mol) and 4-methylmorpholine (7.7 mg, 75.8 μmol) were added and the resulting mixture was stirred at room temperature for 6 hours. Water was added and the mixture was extracted with DCM (3×1.5 mL). The DCM layers were combined, dried over Na₂SO₄, and concentrated to yield a yellow liquid. The crude liquid was purified by reverse phase preparative HPLC to yield the title compound as a white solid (5.1 mg). MS m/z [M+H]⁺ calc'd for C₂₉H₂₆ClNO₁₂, 616.11. found 616.1.

F. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxypentanoic Acid

Ethyl oxalyl chloride (46.1 μL, 0.4 mmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic acid (120 mg, 0.4 mmol) and Et₃N (157 μL, 1.1 mmol) in DMF (2.0 mL, 25.8 mmol) at 0° C., and the resulting mixture was stirred at room temperature for 20 minutes. Additional ethyl oxalyl chloride (30 μL) was added and the mixture was stirred an additional 10 minutes. Water (2 mL) was added and the mixture was extracted with DCM (3×2 mL). The extracts were combined, dried over Na₂SO₄ and concentrated to yield a yellow liquid. The crude liquid was purified by (C-18 column chromatography, 20 g; 40-90% MeCN in water with 0.05% TFA) to yield the title compound (28.5 mg) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₁H₂₂ClNO₆, 420.11. found 420.2.

G. (2R,4R)-5-(3′-Chlorobiphenl-4-yl)-2-hydroxy-4-(isopropoxyoxalylamino)pentanoic Acid

Chloro-oxo-acetic acid isopropyl ester (62.1 mg, 413 μmol;−53 μL) was added dropwise to a solution of (2R,4R)-4-amino-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic acid (100 mg, 313 μmol) and Et₃N (157 μL, 1.1 mmol) in DMF (2.0 mL, 25.8 mmol) at 0° C., and the resulting mixture was stirred at room temperature for 10 minutes. Additional ethyl oxalyl chloride (50 μL) was added and the mixture was stirred an additional 10 minutes. Saturated aqueous NaHCO₃ (5 mL) was added and the mixture was stirred at room temperature for 1 hour. The mixture was extracted with DCM (3×3 mL), the extracts were combined, dried over Na₂SO₄, and concentrated to yield a yellow liquid. The crude liquid was purified (pre HPLC C-18 column chromatography, small column, using 40-95% MeCN in water with 0.05% TFA) to yield the title compound (53.0 mg) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClNO₆, 434.13. found 434.1.

H. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(isobutoxyoxalylamino)pentanoic Acid

1.0 M of aqueous HCL (2.5 mL, 2.5 mmol) was added to (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (100 mg, 287 μmol) and the resulting mixture was stirred at 100° C. for 1 hour. The mixture was concentrated to yield (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid.

Chloro-oxo-acetic acid isobutyl ester (99.4 mg, 604 μmol) was added dropwise to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid and Et₃N (160 μL, 1.2 mmol) in DMF (2.0 mL, 25.8 mmol) at 0° C., and stirred room temperature for 10 minutes. Saturated aqueous NaHCO₃ (5 mL) was added and the mixture was stirred at room temperature for 2 hours. The mixture was extracted with DCM (3×5 mL), the DCM extracts were combined, washed with saturated aqueous NaCl, dried over Na₂SO₄, and concentrated to yield a white solid residue. The crude solid was purified be preparative HPLC C18 column chromatography (small column; 40-90% MeCN in water with 0.05% TFA) to yield the title compound (40.0 mg) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₃H₂₆ClNO₆, 448.14. found 448.1.

I. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Isobutyl Ester

4.0 M HCl in 1,4-dioxane (216 μL, 862 μmol) was added to a suspension of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (75.0 mg, 216 μmol) in isobutyl alcohol (0.5 mL, 5.4 mmol), and the resulting mixture was stirred at 60° C. for 2 hours. The mixture was then concentrated in vacuo to yield a white solid. The white solid was dissolved in DCM and DIPEA (113 μL, 647 μmol) was then added to the mixture followed by ˜0.22 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol) dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.3 mL, 7.7 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (70.5 mg, purity 99%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₃H₂₆ClNO₆, 448.14. found 448.1.

J. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Isopropyl Ester

4.0 M HCl in 1,4-dioxane (216 μL, 862 μmol) was added to a suspension of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (75.0 mg, 216 μmol) in isopropyl alcohol (0.5 mL, 6.5 mmol) and the resulting mixture was stirred at 60° C. overnight. The mixture was then concentrated in vacuo to yield a white solid. The white solid was dissolved in DCM and DIPEA (113 μL, 647 μmol) was then added to the mixture followed by ˜0.22 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol) dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.3 mL, 7.7 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (62.8 mg, purity 98%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClNO₆, 434.13. found 434.1.

K. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Heptyl Ester

4.0 M HCl in 1,4-dioxane (216 μL, 862 μmol) was added to a suspension of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (75.0 mg, 216 μmol) in 1-heptanol (250 μL, 1.8 mmol) and the resulting mixture was stirred at 60° C. for 2 hours. The mixture was then concentrated in vacuo to yield a white solid, which was purified (Interchim reverse phase chromatography column; 30-90% MeCN in water gradient with 0.5% TFA). The purified white solid was dissolved in DCM and DIPEA (113 μL, 647 μmol) was then added to the mixture followed by ˜0.22 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol) dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.3 mL, 7.7 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (43.3 mg, purity 99%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₆H₃₂ClNO₆, 490.19. found 490.2.

L. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid 3,3,3-Trifluoropropyl Ester

4.0 M HCl in 1,4-dioxane (287 μL, 1.2 mmol) was added to a suspension of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (50.0 mg, 144 μmol) in 3,3,3-trifluoropropan-1-ol (492 mg, 4.3 mmol) and the resulting mixture was stirred at 80° C. for 12 hours. The mixture was then concentrated in vacuo to yield a white solid, which was dissolved in DCM (1.0 mL) and ˜0.2 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol). DIPEA (75.1 μL, 431 μmol) was then added dropwise and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.3 mL, 7.7 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (44.9 mg, purity 99%) as white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₂₁ClF₃NO₆, 488.10. found 488.1.

M. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid 2,2,2-Trifluoroethyl Ester

4.0 M HCl in 1,4-dioxane (287 μL, 1.2 mmol) was added to a suspension of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (50.0 mg, 144 μmol) in 2,2,2-trifluoroethanol (0.5 mL, 6.9 mmol) and the resulting mixture was stirred at 110° C. for 12 hours. The mixture was then concentrated in vacuo to yield a white solid, which was dissolved in DCM (1.0 mL) and ˜0.2 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol). DIPEA (75.1 μL, 431 μmol) was then added dropwise and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.3 mL, 7.7 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (22.5 mg, purity 98%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₁H₁₉ClF₃NO₆, 474.09. found 474.1.

N. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-[(3,3,3-trifluoropropoxyoxalyl)-amino]pentanoic Acid

Benzyl alcohol (13.0 mL, 126 mmol) was added to (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (1.9 g, 5.3 mmol) followed by 4.0 M HCl in 1,4-dioxane (5.3 mL, 21.3 mmol), and the mixture was stirred at 60° C. for 1 hour. The mixture was purified (Interchim reverse phase chromatography column; 30-90% MeCN in water with 0.05% TFA) to yield (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid benzyl ester (2.2 g) as a white solid. (evaporated in vacuo with water (4×300 mL) to remove excess benzyl alcohol).

3,3,3-trifluoropropyl oxalyl chloride was prepared by adding oxalyl chloride (51.6 μL, 610 μmol) to a solution of 3,3,3-trifluoropropan-1-ol (62.6 mg, 549 μmol) in ether (500 μL, 4.8 mmol). The resulting mixture was stirred at room temperature for 1 hour and then concentrated in vacuo yield a clear colorless liquid. A ˜1M solution of the oxalyl chloride was prepared by dissolving the resulting liquid in ˜0.61 mL DCM.

A 3,3,3-trifluoropropyl oxalyl chloride solution (˜140 μL) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid benzyl ester (50.0 mg, 122 μmol) in DCM (1.0 mL) at 0 OC, and the mixture was stirred at 0° C. for 15 minutes. Saturated aqueous NaHCO₃ (1 mL) was added and the mixture was stirred at room temperature for 1 hour. The layers were separated and the aqueous layer was extracted with DCM (2×2 mL). The DCM layers were combined, dried over Na₂SO₄, and concentrated to yield a clear yellow liquid. 10% Pd/C, 50% wet (0.45 mmol/g loading; 13.6 mg, 6.1 μmol) was added to a solution of the yellow liquid in DCM and THF (1.0 mL), and the mixture was stirred under hydrogen for 30 minutes. The mixture was filtered and the filtrate was concentrated to yield a clear yellow liquid. The crude liquid was purified by preparative HPLC (40-90% MeCN in water with 0.05% TFA) to yield the title compound (16.5 mg, purity 99%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₂₁ClF₃NO₆, 488.10. found 4880.

O. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid 2,2,3,3,3-Pentafluoropropyl Ester

A ˜1M solution of t-butyl oxalyl chloride (˜0.2 mL) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid 2,2,3,3,3-pentafluoropropyl ester (50.0 mg, 111 μmol) in DCM (1.0 mL) at 0° C. followed by the dropwise addition over 10 minutes of DIPEA (21.2 μL, 122 μmol). The mixture was stirred at 0° C. for 15 minutes. Saturated aqueous NaHCO₃ (5 mL) was added and the mixture was extracted with DCM (3×5 mL). The DCM extracts were combined, dried over Na₂SO₄, and concentrated to yield a clear colorless liquid. The crude liquid was purified by flash chromatography (50% EtOAc/hexanes to yield a clear colorless liquid. 1:1 TFA/DCM (1.0 mL) was added to a solution of the colorless liquid and stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified preparative HPLC (40%-90% MeCN in water with 0.05% TFA) to yield the title compound (21.6 mg, purity 98%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₁₉ClF₅NO₆, 524.08. found 524.0.

P. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid 5-Methyl-2-oxo-[1,3]dioxol-4-ylmethyl Ester

A ˜1M solution of t-butyl oxalyl chloride (160 μL) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid 5-methyl-2-oxo[1,3]dioxol-4-ylmethyl ester (50.0 mg, 116 μmol) in DCM (1.00 mL, 15.6 mmol) at 0° C. followed by the dropwise addition over 10 minutes of N,N-diisopropylamine (17.8 μL, 127 μmol). The resulting mixture was stirred at 0° C. for 15 minutes, then concentrated in vacuo. 1:1 TFA/DCM (1.0 mL, 6.2 mmol) was added to the residue and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale C18 column chromatography, small column, using 30-90% MeCN in water with 0.05% TFA) to yield the title compound as a white solid (9.6 mg). MS m/z [M+H]⁺ calc'd for C₂₄H₂₂ClNO₉, 504.10. found 504.0.

Q. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Butyryloxymethyl Ester

A ˜1M solution of t-butyl oxalyl chloride (160 μL) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid butyryloxymethyl ester (48.6 mg, 116 μmol) in DCM (1.00 mL, 15.6 mmol) at 0° C. followed by the dropwise addition over 10 minutes of N,N-diisopropylamine (17.8 μL, 127 μmol). The resulting mixture was stirred at 0° C. for 15 minutes, then concentrated in vacuo. 1:1 TFA/DCM (1.0 mL, 6.2 mmol) was added to the residue and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale C18 column chromatography, small column, using 30-90% MeCN in water with 0.05% TFA) to yield the title compound as a white solid (10.2 mg). MS m/z [M+H]⁺ calc'd for C₂₄H₂₆ClNO₈, 492.13. found 492.0.

R. (2R,4R)-5-(3′-Chloro-biphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Acetoxymethyl Ester

To a solution of (2R,4R)-4-(t-butoxyoxalylamino)-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid (200 mg, 450 μmol) and bromomethyl acetate (97 mg, 0.9 mmol) in DMF (2 mL) was added 2,6-lutidine (144 mg, 1.3 mmol) and NaI (67 mg, 450 μmol). After stirring at room temperature for 24 hours, the mixture was diluted with water (20 mL) and extracted with EtOAc (2×20 mL). The combined organic layers were washed with saturated aqueous NaCl (2×70 mL), dried over anhydrous Na₂SO₄, filtered, and concentrated to give the crude product which was further purified by preparative TLC (PE:EtOAc=2:1) to yield Compound 1 (100 mg) as a yellow solid. LC-MS: 542[M+Na]⁺.

To a solution of Compound 1 (100 mg, 0.2 mmol) in DCM (5 mL) was added TFA (2 mL) at 0° C. The mixture was stirred at room temperature for 2 hours, the solvent was removed, and the residue was further purified by preparative TLC (DCM:MeOH=8:1) to yield the title compound as a white solid (10 mg). LC-MS: 464[M+H]. ¹H NMR (400 MHz, MeOD) δ 7.61 (s, 1H), 7.55 (d, J=8.0 Hz, 3H), 7.42 (t, J=7.8 Hz, 1H), 7.34 (d, J=8.1 Hz, 3H), 5.78 (s, 2H), 4.40 (s, 1H), 4.31 (t, J=5.9 Hz, 1H), 2.94 (ddd, J=22.0, 13.8, 7.2 Hz, 2H), 2.09 (m, 5H).

S. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Ethoxycarbonyloxymethyl Ester

To a solution of (2R,4R)-4-(t-butoxyoxalylamino)-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid (100 mg, 220 μmol) and chloromethyl ethyl carbonate (61 mg, 440 μmol) in DMF (3 mL) was added 2,6-lutidine (72 mg, 660 μmol) and NaI (33 mg, 220 μmol). After stirring at room temperature for 24 hours, the mixture was diluted with water (20 mL) and extracted with EtOAc (2×20 mL). The combined organic layers were washed with saturated aqueous NaCl (2×70 mL), dried over anhydrous Na₂SO₄, filtered, and concentrated to give the crude product which was further purified by preparative TLC (PE:EtOAc=2:1) to yield Compound 1 (40 mg) as a yellow solid. LC-MS: 572[M+Na]⁺.

To a solution of Compound 1 (40 mg, 70 μmol) in DCM (3 mL) was added TFA (1 mL) at 0° C. The mixture was stirred at room temperature for 2 hours, the solvent was removed, and the residue was further purified by preparative TLC (DCM:MeOH=8:1) to yield the title compound as a white solid (18 mg). LC-MS: 494[M+H]⁺. ¹H NMR (400 MHz, MeOD) δ 7.55 (m, 4H), 7.38 (m, 4H), 5.80 (d, J=18.6 Hz, 2H), 4.34 (s, 2H), 4.21 (dd, J=14.3, 7.1 Hz, 2H), 2.95 (m, 2H), 2.07 (d, J=28.0 Hz, 2H), 1.29 (dd, J=12.6, 5.5 Hz, 3H). MS m/z [M+H]⁺ calc'd for C₂₃H₂₄ClNO₉, 494.11. found 494.

T. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-[(2-methoxyethoxyoxalyl)amino]-pentanoic Acid

DIPEA (64 μL, 366 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid benzyl ester (50.0 mg, 122 μmol) in DCM (3 mL) followed by the dropwise addition of a 1.0M chloro-oxo-acetic acid 2-methoxyethyl ester (22 mg, 134 μmol) solution in DCM. The resulting mixture was stirred at room temperature for 30 minutes, then concentrated to yield a clear yellow liquid. The crude liquid was purified (Interchim C18 chromatography column, 20 g, 340-90% MeCN in water with 0.05% TFA). THF (3 mL) was added to the purified material, followed by the addition of palladium carbon (10 wt % on carbon, wet 50 g, 12.9 mg, 12 μmol) and the mixture was stirred under hydrogen for 30 minutes. The mixture was filtered and concentrated in vacuo, and the residue dissolved in AcOH (0.5 mL) and purified by preparative HPLC to yield the title compound (9.8 mg). MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClNO₇, 450.12. found 450.2.

U. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-[(2-phenoxyethoxyoxalyl)amino]-pentanoic Acid

DIPEA (64 μL, 366 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid benzyl ester (50.0 mg, 122 μmol) in DCM (3 mL) followed by the dropwise addition of a 1.0M chloro-oxo-acetic acid 2-phenoxyethyl ester (31 mg, 134 μmol) solution in DCM. The resulting mixture was stirred at room temperature for 30 minutes, then concentrated to yield a clear yellow liquid. The crude liquid was purified (Interchim C18 chromatography column, 20 g, 340-90% MeCN in water with 0.05% TFA). THF (3 mL) was added to the purified material, followed by the addition of palladium carbon (10 wt % on carbon, wet 50 g, 12.9 mg, 12 μmol) and the mixture was stirred under hydrogen for 30 minutes. The mixture was filtered and concentrated in vacuo, and the residue dissolved in AcOH (0.5 mL) and purified by preparative HPLC to yield the title compound (3.5 mg). MS m/z [M+H]⁺ calc'd for C₂₇H₂₆ClNO₇, 512.14. found 512.2.

V. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-4-[(3-ethoxypropoxyoxalyl)amino]-2-hydroxy-pentanoic Acid

DIPEA (64 μL, 366 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid benzyl ester (50.0 mg, 122 μmol) in DCM (3 mL) followed by the dropwise addition of a 1.0M chloro-oxo-acetic acid 3-ethoxypropyl ester (26 g, 134 μmol) solution in DCM. The resulting mixture was stirred at room temperature for 30 minutes, then concentrated to yield a clear yellow liquid. The crude liquid was purified (Interchim C18 chromatography column, 20 g, 340-90% MeCN in water with 0.05% TFA). THF (3 mL) was added to the purified material, followed by the addition of palladium carbon (10 wt % on carbon, wet 50 g, 12.9 mg, 12 μmol) and the mixture was stirred under hydrogen for 30 minutes. The mixture was filtered and concentrated in vacuo, and the residue dissolved in AcOH (0.5 mL) and purified by preparative HPLC to yield the title compound (10.5 mg). MS m/z [M+H]⁺ calc'd for C₂₄H₂₈ClNO₇, 478.16. found 478.2.

W. (2R,4R)-5-(3′-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid (S)-2-Methoxycarbonylamino-3-methylbutryloxymethyl Ester

Following the methods described herein, the title compound was also prepared (12.6 mg). MS m/z [M+H]⁺ calc'd for C₂₇H₃₁ClN₂O₁₀, 579.17. found 579.2

Example 3 A. (2R,4R)-5-(2′,5′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid

A solution of ethyl oxalyl chloride (42.4 μL, 0.4 mmol) in DCM (0.4 mL, 6 mmol) was added to a solution of (2R,4R)-4-amino-5-(4-bromophenyl)-2-hydroxypentanoic acid ethyl ester (80 mg, 0.2 mmol) and Et₃N (0.1 mL, 0.8 mmol) in DCM (1 mL), and the resulting mixture was stirred at room temperature for 30 minutes, then evaporated under reduced pressure. The product was then combined with 2,5-dichlorophenylboronic acid (72.4 mg, 0.4 mmol), K₂CO₃ (104.9 mg, 759 μmol), EtOH (0.9 mL), and water (0.2 mL). The mixture was placed under nitrogen and SilicaCat® DPP-Pd (0.28 mmol/g loading, 90.4 mg, 25.3 μmol) was added. The mixture was microwaved at 120° C. for 20 minutes, then filtered. 1 M Aqueous LiOH (2.5 mL, 2.5 mmol) was added to yield the title compound (11.9 mg, purity 100%). MS m/z [M+H]⁺ calc'd for C₁₉H₁₇Cl₂NO₆, 426.04. found 426.0.

B. (2R,4R)-5-(2′,5′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid Isobutyl Ester

4.0 M HCl in 1,4-dioxane (196 μL, 785 μmol) was added to a suspension of (2R,4R)-4-amino-5-(2′,5′-dichlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid ethyl ester (75.0 mg, 196 μmol) in isobutyl alcohol (0.5 mL, 5.4 mmol), and the resulting mixture was stirred at 60° C. for 2 hours. The mixture was then concentrated in vacuo to yield a white solid. The white solid was dissolved in DCM (1 mL) and DIPEA (102 μL, 588 μmol) was then added to the mixture followed by ˜0.2 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol) dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.1 mL, 7.0 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (80 mg, purity 99%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₃H₂₅Cl₂NO₆, 482.11. found 482.1.

C. (2R,4R)-5-(2′,5′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid

4.0 M HCl in 1,4-dioxane (196 μL, 785 μmol) was added to a suspension of (2R,4R)-4-amino-5-(2′,5′-dichlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid ethyl ester (75.0 mg, 196 μmol) in isopropyl alcohol (0.5 mL, 6.5 mmol), and the resulting mixture was stirred at 60° C. overnight. The mixture was then concentrated in vacuo to yield a white solid. The white solid was dissolved in DCM (1 mL) and DIPEA (102 μL, 588 μmol) was then added to the mixture followed by ˜0.2 mL of a 1M t-butyl oxalyl chloride solution in DCM (0.2 mmol) dropwise. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a yellow liquid. A TFA/DCM (1:1, 1.1 mL, 7.0 mmol) solution was added to the yellow liquid and the resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo to yield a clear yellow liquid. The crude liquid was purified (preparative scale HPLC C18 column chromatography, 40-90% MeCN in water with 0.05% TFA) to yield the title compound (60.6 mg, purity 98%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₂H₂₃Cl₂NO₆, 468.09. found 468.1.

D. (2R,4R)-5-(2′,5′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(isobutoxyoxalylamino)-pentanoic Acid

1.0 M Aqueous HCl (3.5 mL, 3.5 mmol) was added to (2R,4R)-4-amino-5-(2′,5′-dichlorobiphenyl-4-yl)-2-hydroxy-pentanoic acid ethyl ester (155 mg, 405 μmol) and the mixture was stirred at 100° C. for 1 hour then concentrated. The product was combined with Et₃N (226 μL, 1.6 mmol) in DMF (2.5 mL, 32.3 mmol). Chloro-oxo-acetic acid isobutyl ester (140 mg, 851 μmol) was added dropwise at 0° C. and the resulting mixture was stirred at room temperature for 10 minutes. Saturated aqueous NaHCO₃ (5 mL) was added and the mixture was stirred at room temperature for 2 hours. The mixture was extracted with DCM (3×5 mL), the extracts were combined, washed with a saturated aqueous NaCl solution, dried over Na₂SO₄ and concentrated to yield a white solid residue. The crude solid was purified via preparative HPLC (C18 column; 40-90% MeCN in water with 0.05% TFA) to yield the title compound (98.0 mg, purity 99%) as a white solid. MS m/z [M+H]⁺ calc'd for C₂₃H₂₅Cl₂NO₆, 482.11. found 482.1.

Example 4 (2R,4R)-5-(3-Chlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic Acid

A solution of ethyl oxalyl chloride (41 μL, 0.4 mmol) in DCM (0.5 mL) was added to a solution of (3R,5R)-5-amino-6-(4-bromo-2-chloro-phenyl)-2-ethoxy-hex-1-en-3-ol (96 mg, 0.3 mmol) and Et₃N (0.1192 mL, 0.8556 mmol) in DCM (1.4 mL), and stirred for 20 minutes at room temperature. The mixture was evaporated under reduced pressure and combined with phenylboronic acid (52.2 mg, 0.4 mmol), K₂CO₃ (100 mg, 0.9 mmol), water (0.2 mL), and EtOH (1 mL). The resulting mixture was placed under nitrogen, and SilicaCat® DPP-Pd (0.28 mmol/g loading; 100 mg, 0.03 mmol) was added. The mixture was heated at 120° C. for 20 minutes until the reaction was complete. The mixture was filtered and a solution of 1 M aqueous LiOH (3 mL, 3 mmol) was added. The product was then purified (Interchim reverse phase chromatography column) to yield the title compound (12.6 mg). MS m/z [M+H]⁺ calc'd for C₁₉H₁₈ClNO₆, 392.08. found 392.2.

Example 5

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, the following compounds were prepared:

MS m/z: [M + H]⁺ Ex. R¹ a R⁵ b R⁶ Formula calcd found 1 H 0 — 2 2′-CH₃, 5′-Cl C₂₀H₂₀ClNO₆ 406.10 406.0 2 —CH—(CH₃)₂ 0 — 2 2′-CH₃, 5′-Cl C₂₃H₂₆ClNO₆ 448.14 448.0 3 —CH₂CH₃ 0 — 2 2′-CH₃, 5′-Cl C₂₂H₂₄ClNO₆ 434.13 434.4 4 —CH₂—CH—(CH₃)₂ 0 — 2 2′-CH₃, 5′-Cl C₂₄H₂₈ClNO₆ 462.16 462.0 5 H 0 — 2 2′-F, 5′-Cl C₁₉H₁₇ClFNO₆ 410.07 410.0 6 —CH₂CH₃ 0 — 2 2′-F, 5′-Cl C₂₁H₂₁ClFNO₆ 438.10 438.0 7 —CH₂CH—(CH₃)₂ 0 — 2 2′-F, 5′-Cl C₂₃H₂₅ClFNO₆ 466.14 466.0 8 —CH—(CH₃)₂ 0 — 2 2′-F, 5′-Cl C₂₂H₂₃ClFNO₆ 452.12 452.0 9 H 1 3-Cl 1 3′-Cl C₁₉H₁₇Cl₂NO₆ 426.04 426.0 10 —CH₂CH₃ 1 3-Cl 1 3′-Cl C₂₁H₂₁Cl₂NO₆ 454.07 454.0 11 —CH₂CH—(CH₃)₂ 1 3-Cl 1 3′-Cl C₂₃H₂₅Cl₂NO₆ 482.11 482.0 12 —CH—(CH₃)₂ 1 3-Cl 1 3′-Cl C₂₂H₂₃Cl₂NO₆ 468.09 468.1 13 H 1 3-Cl 2 2′-F, 5′-Cl C₁₈H₁₅Cl₂FN₂O₆ 445.03 445.0 1. (2R, 4R)-5-(5′-Chloro-2′-methylbiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)-pentanoic acid 2. (2R, 4R)-5-(5′-Chloro-2′-methylbiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)-pentanoic acid isopropyl ester 3. (2R, 4R)-5-(5′-Chloro-2′-methylbiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid ethyl ester 4. (2R, 4R)-5-(5′-Chloro-2′-methylbiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid isobutyl ester 5. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid 6. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid ethyl ester 7. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid isobutyl ester 8. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid isopropyl ester 9. (2R, 4R)-5-(3,3′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid 10. (2R, 4R)-5-(3,3′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(isobutoxyoxalylamino)- pentanoic acid 11. (2R, 4R)-5-(3,3′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid isobutyl ester 12. (2R, 4R)-5-(3,3′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid isopropyl ester 13. (R)-3-[N-(3,5′-Dichloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalyl-hydrazino]-2-hydroxypropionic acid

MS m/z: [M + H]⁺ Ex. R⁴ a R⁵ b R⁶ Formula calcd found 14 —CH₂CH₃ 0 — 2 2′-F, 5′-Cl C₂₁H₂₁ClFNO₆ 438.10 438.2 15 —CH—(CH₃)₂ 0 — 2 2′-F, 5′-Cl C₂₂H₂₃ClFNO₆ 452.12 452.2 16 —CH₂CH—(CH₃)₂ 0 — 2 2′-F, 5′-Cl C₂₃H₂₅ClFNO₆ 466.14 466.4 17 —CH₂CH—(CH₃)₂ 1 3-Cl 1 3′-Cl C₂₃H₂₅Cl₂NO₆ 482.11 482.1 14. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-4-(ethoxyoxalylamino)-2-hydroxy-pentanoic acid 15. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(isopropoxyoxalyl-amino)-pentanoic acid 16. (2R, 4R)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxy-4-(isobutoxyoxalylamino)-pentanoic acid 17. (2R, 4R)-5-(3,3′-Dichlorobiphenyl-4-yl)-2-hydroxy-4-(oxalylamino)pentanoic acid ethyl ester

Example 6 A. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-(oxalylamino)pentanoic Acid

Ethyl oxalyl chloride (27 μL, 0.2 mmol, 1.1 eq) was added to a solution of (2S,4S)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid ethyl ester (HCl salt; 80 mg, 0.22 mmol) in DMF (0.5 mL)/DCM (0.5 mL), and stirred at room temperature for 20 minutes. The solvent was removed and the residue was dissolved in LiOH (monohydrate; 92.2 mg, 2.2 mmol), water (1.0 mL) and EtOH (2.0 mL), and stirred at room temperature for 30 minutes. The reaction was quenched with AcOH and the solvent was removed. The residue was dissolved into AcOH/MeCN and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (37 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₀H₂₁NO₆, 372.14. found 372.2.

B. (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-4-(oxalylamino)pentanoic Acid Ethyl Ester

Oxalyl chloride (232 μL, 2.8 mmol) and t-butyl alcohol (228 μL) were combined in ether (6.7 mL) under nitrogen at 0° C. The resulting mixture was stirred for 30 minutes at room temperature. The solvent was evaporated under vacuum to form chloro-oxo-acetic acid t-butyl ester, which was then dissolved in DCM (10 mL) and combined with (2S,4S)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid ethyl ester (HCl salt; 667 mg, 1.8 mmol), which had been dissolved in DCM with Et₃N (2.6 mL) at 0° C. The resulting mixture was stirred for 5 minutes at room temperature. The crude product was concentrated, dissolved in DCM and purified by flash chromatography (20-80% EtOAc/hexanes). The solvent was removed and the residue was dissolved in DCM (5 mL) and TFA (1 mL), and stirred for 1 hour. The product was dried under vacuum and purified by preparative HPLC to yield the title compound (135 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₂H₂₅NO₆, 400.17. found 400.2.

Example 7 A. (2S,4S)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic Acid Butyl Ester

Oxalyl chloride (44.1 μL. 0.5 mmol) and t-butyl alcohol (46.5 μL) were combined in ether (1 mL) and was stirred for 30 minutes at room temperature. The solvent was evaporated under vacuum to form chloro-oxo-acetic acid t-butyl ester, which was then dissolved in DCM (2 mL). (2S,4S)-4-amino-5-(2′-fluorobiphenyl-4-yl)-2-hydroxymethylpentanoic acid ethyl ester (HCl salt; 120 mg, 0.3 mmol) was combined with 1-butanol (3 mL) and 4 M of HCl in 1,4-dioxane (3 mL) and stirred at 60° C. for 2 hours. The solvent were evaporated and azeotroped with toluene (2×). and the product was dissolved in Et₃N (155 μL) and DCM, then combined with the chloro-oxo-acetic acid t-butyl ester. The resulting mixture was stirred for 20 minutes at room temperature. The solvent was evaporated and the residue was redissolved in 1:1 TFA:DCM, and stirred for 20 minutes at 40° C. AcOH was added and the product was purified by preparative HPLC to yield the title compound (30 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₄H₂₈FNO₆, 446.19. found 446.4.

B. (2S,4S)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic Acid

Ethyl oxalyl chloride (13.8 μL, 0.1 mmol) and DIPEA (39.2 μL, 0.2 mmol) were combined with (2S,4S)-4-amino-5-(2′-fluorobiphenyl-4-yl)-2-hydroxymethylpentanoic acid ethyl ester (HCl salt; 43 mg, 0.1 mmol) dissolved in DCM (0.9 mL). The mixture was stirred at room temperature for 10 minutes, then concentrated under vacuum. 1 M aqueous LiOH (0.9 mL) and EtOH (0.9 mL) was added and the resulting mixture was stirred at room temperature for 1 hour. The reaction mixture was quenched with AcOH and the solvent was evaporated. The residue was dissolved in AcOH/MeCN and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (32.7 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₀H₂₀FNO₆, 390.13. found 390.2.

Example 8

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, the following compound were prepared:

MS m/z: [M + H]⁺ Ex. R¹ R⁶ Formula calcd found 1 —CH₂CH₃ F C₂₂H₂₄FNO₆ 418.16 418.4 2 H F C₂₀H₂₀FNO₆ 390.13 390.4 3 H Cl C₂₀H₂₀ClNO₆ 406.10 406.4 1. (2S, 4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid ethyl ester 2. (2S, 4S)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid 3. (2S, 4S) -5-(3′-Chlorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid

MS m/z: [M + H]⁺ Ex. R¹ R⁶ Formula calcd found 4 H F C₂₀H₂₀FNO₆ 390.13 390.2 4. (2S, 4S)-5-(4′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid

MS m/z: [M +H]⁺ Ex. R¹ R⁵ Formula calcd found 5 H Cl C₂₀H₂₀ClNO₆ 406.10 406.0 6 H Cl C₂₀H₂₀ClNO₆ 406.10 406.0 5. (2S, 4S)-5-(3-Chlorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid 6. (2R, 4S)-5-(3-Chlorobiphenyl-4-yl)-2-hydroxymethyl-4-(oxalylamino)pentanoic acid

Example 9 A. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic Acid

Ethyl oxalyl chloride (13.1 μL, 0.1 mmol) was combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methylpentanoic acid ethyl ester (40 mg, 0.1 mmol) dissolved in DCM (0.3 mL) and a small amount of DMF. The mixture was stirred at room temperature for 20 minutes, then concentrated under vacuum. 1 M aqueous NaOH (117 μL) and THF (1.5 mL) was added and the resulting mixture was stirred at room temperature for 30 minutes. The residue was dissolved in AcOH and purified by preparative HPLC to yield the title compound (8 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₁H₂₃NO₆, 386.15. found 386.0.

B. (2S,4R)-5-Biphenyl-4-yl-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic Acid Ethyl Ester

Oxalyl chloride (12.4 μL. 0.1 mmol) and t-butyl alcohol (13.1 μL) were combined in ether (0.3 mL) under nitrogen at 0° C. The resulting mixture was stirred for 30 minutes at room temperature. The solvent was evaporated under vacuum to form chloro-oxo-acetic acid t-butyl ester, which was then dissolved in DCM (0.7 mL) and combined with (2S,4R)-4-amino-5-biphenyl-4-yl-2-hydroxymethyl-2-methylpentanoic acid ethyl ester (33.4 mg, 98 μmol). Et₃N (43.6 μL,) at 0° C. was added and the resulting mixture was stirred for 30 minutes at room temperature. The solvent were evaporated and the residue was dissolved in 1:1 TFA:DCM and stirred for 1 hour. AcOH was added and the product was purified by preparative HPLC to yield the title compound (7 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₃H₂₇NO₆, 414.18. found 414.4.

Example 10 (2S,4R)-5-(3′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic Acid

Ethyl oxalyl chloride (9.1 μL, 0.1 mmol) was combined with (2S,4R)-4-amino-5-(3′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methylpentanoic acid (27 mg, 0.1 mmol) dissolved in DCM (0.2 mL) and a small amount of DMF. The mixture was stirred at room temperature for 20 minutes. The solvent was evaporated amd 10 M aqueous NaOH (81.5 μL), and THF (1.0 mL) was added and the resulting mixture was stirred at room temperature for 30 minutes. The residue was dissolved in AcOH and purified by preparative HPLC to yield the title compound (6 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₁H₂₂FNO₆, 404.14. found 404.4.

Example 11

Following the procedures described in the examples herein, and substituting the appropriate starting materials and reagents, the following compounds were prepared:

MS m/z: [M + H]⁺ Ex. b R⁶ Formula calcd found 1 1 2′-F C₂₁H₂₂FNO₆ 404.14 404.4 2 2 2′-F, 5′-Cl C₂₁H₂₁ClFNO₆ 438.10 438.2 1. (2S, 4R)-5-(2′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic acid 2. (2R, 4S)-5-(5′-Chloro-2′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic acid

MS m/z: [M + H]⁺ Ex. R⁶ Formula calcd found 3 F C₂₁H₂₂FNO₆ 404.14 404.4 3. (2S, 4R)-5-(4′-Fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-(oxalylamino)pentanoic acid

MS m/z: [M + H]⁺ Ex. R⁶ Formula calcd found 4 Cl C₂₅H₃₀ClNO₆ 476.18 476.2 4. (2S, 4R)-5-(3 ′-Chlorobiphenyl-4-yl)-2-hydroxymethyl-4-(isobutoxyoxalyl-amino)-2- methylpentanoic acid

Example 12 3-(N-Biphenyl-4-ylmethyl-N′-oxalylhydrazino)-2-hydroxy-2-methylpropionic Acid

3-(N-Biphenyl-4-ylmethyl-N′-t-butoxycarbonylhydrazino)-2-hydroxy-2-methylpropionic acid methyl ester (0.1 g, 241 μmol) was dissolved in DCM (1.0 mL), then TFA (1.0 mL) was added and the mixture was stirred at room temperature for 1 hour. The mixture was concentrated and the residue was dissolved in DMF (2.00 mL). DIPEA (126 μL, 724 μmol) was added followed by ethyl oxalyl chloride (29.6 μL, 265 μmol) and the resulting mixture was stirred at room temperature until the reaction was complete (˜3 hours). The mixture was concentrated and the residue was dissolved in THF (1.5 mL), then lithium hydroxide monohydrate (101 mg, 2.4 mmol) in water (1.50 mL) was added and the mixture was stirred at room temperature for 30 minutes. The reaction was quenched with AcOH and the solution was concentrated. The crude product was purified by preparative HPLC (10-70% MeCN/H₂O) to yield the title compound (10.9 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₁₉H₂₀N₂O₆, 373.13. found 373.2.

Example 13 (R)-3-[N-(3′-Chlorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid

(R)-3-[N-(3′-Chlorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxy-propionic acid ethyl ester (70 mg, 0.2 mmol) was dissolved in DCM (1.5 mL), followed by the addition of ethyl oxalyl chloride (24.7 μL, 221 μmol) and DIPEA (69.9 μL, 401 μmol). The mixture was stirred at room temperature until the reaction was complete (˜10 minutes). The mixture was the concentrated under vacuum. 1 M aqueous lithium hydroxide (1.6 mL, 1.6 mmol) and EtOH (1.5 mL) was added and the mixture was stirred at room temperature until the reaction was complete (˜2 hours). The reaction was quenched with AcOH and the solvent was evaporated. The residue was dissolved in AcOH/MeCN and purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (8.3 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₁₈H₁₇ClN₂O₆, 393.08. found 393.2.

Example 14 A. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid

Oxalic acid (R)-2-[N-(4-bromobenzyl)-N′-ethoxyoxalylhydrazino]-1-ethoxycarbonylethyl ester ethyl ester (675 mg, 1.3 mmol) was combined with 5-chloro-2-fluorophenylboronic acid (273 mg, 1.6 mmol) and K₂CO₃ (541 mg, 3.9 mmol) in EtOH (4.6 mL, 78.3 mmol) and water (1.2 mL, 65.2 mmol). The resulting mixture was placed under nitrogen atmosphere and SilicaCat® DPP-Pd (0.28 mmol/g loading; 466 mg, 130 mol) was then added. The mixture was microwaved at 120° C. for 10 minutes, then filtered and evaporated under reduced pressure. The residue was purified by preparative HPLC to yield the title compound (40 mg). MS m/z [M+H]⁺ calc'd for C₁₈H₁₆ClFN₂O₆, 411.07. found 411.0.

B. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid Ethyl Ester

A ˜1M solution of t-butyl oxalyl chloride in DCM (136 μL) was added to a stirred solution of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid ethyl ester (HCl salt; 55.0 mg, 136 μmol) in DCM (1.3 mL, 20 mmol) at 0° C. After stirring at room temperature for 2 hours, DIPEA (11.9 μL, 68 μmol) in a DCM solution (80 μL) was added dropwise. After one minute, additional DIPEA (10 μL) in DCM (80 μL) was added, and the mixture was stirred at room temperature overnight. The mixture was concentrated and the resulting residue was purified by purified by flash chromatography (4 g silica gel, 0-100% EtOAc/hexanes). The desired fractions were combined and concentrated to yield a colorless oil (60 mg). A portion of this oil (20 mg) was treated with a 1:1 mixture of DCM:TFA (0.2 mL) at room temperature for 20 minutes. The mixture was concentrated, the residue was dissolved in 50% water/AcOH (1.5 mL), filtered, and purified by reverse phase preparative to yield the title compound (10 mg) as a TFA salt. MS m/z [M+H]⁺ calc'd for C₂₀H₂₀ClFN₂O₆, 439.10. found 439.4.

C. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-isobutoxyoxalyhydrazino]-2-hydroxypropionic Acid

Chloro-oxo-acetic acid isobutyl ester was prepared by adding oxalyl chloride (21 μL, 252 μmol) to a solution of isobutanol (21 μL, 226 μmol) in ether (206 μL, 2.0 mmol). The mixture was stirred at room temperature for 15 min and then evaporated.

The chloro-oxo-acetic acid isobutyl ester was then added to a solution of (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (23.0 mg, 50 μmol) in DCM (413 μL, 6.4 mmol) at 0° C. The resulting mixture was stirred at 0° C. for 15 minutes. Saturated aqueous NaHCO₃ was then added and the layers were separated. The aqueous layer was extracted with DCM. The DCM layers were combined, dried over MgSO₄ and concentrated to yield a clear yellow liquid. Zinc (164 mg, 2.5 mmol) was added to a solution of this yellow liquid in AcOH (172 μL, 3.0 mmol) and the mixture was stirred at room temperature for 10 minutes. The mixture was filtrated using AcOH and water, the solvents were evaporated in vacuo, and the residue was purified by preparative HPLC to yield the title compound (9.0 mg). MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClFN₂O₆, 467.13. found 467.1

D. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-methyl)-N′-(2,2-difluoropropoxyoxalyl)-hydrazino]-2-hydroxypropionic Acid

2,2-Difluoropropyl oxalyl chloride was prepared by adding oxalyl chloride (21 μL, 252 μmol) to a solution of 2,2-difluoropropanol (21.8 mg, 226 μmol) in ether (206 μL, 2.0 mmol). The mixture was stirred at room temperature for 15 minutes and then evaporated.

The 2,2-difluoropropyl oxalyl chloride was then added to a solution of (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (23.0 mg, 50 μmol) in DCM (413 μL, 6.4 mmol) at 0° C. The resulting mixture was stirred at 0° C. for 15 minutes. Saturated aqueous NaHCO₃ was then added and the layers were separated. The aqueous layer was extracted with DCM. The DCM layers were combined, dried over MgSO₄, and concentrated to yield a clear yellow liquid. Zinc (164 mg, 2.5 mmol) was added to a solution of this yellow liquid in AcOH (172 μL, 3.0 mmol) and the mixture was stirred at room temperature for 10 minutes. The mixture was filtrated using AcOH and water, the solvents were evaporated in vacuo, and the residue was purified by preparative HPLC to yield the title compound (1.1 mg). MS m/z [M+H]⁺ calc'd for C₂₁H₂₀ClF₃N₂O₆, 489.10. found 489.0.

E. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalyl-hydrazino]-2-hydroxypropionic acid 5-Methyl-2-oxo-[1,3]dioxol-4-ylmethyl Ester

To a solution of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 5-methyl-2-oxo-[1,3]dioxol-4-ylmethyl ester (350 mg, 780 μmol) in anhydrous DCM (15 mL) was added t-butyl oxalyl chloride (193 mg, 1.2 mmol) and DIPEA (302 mg, 2.3 mmol) at 0° C. The resulting mixture was stirred at room temperature for 5 hours. The mixture was then washed with saturated aqueous NaCl (2×30 mL) and extracted with DCM (3×50 mL). The combined organic layers were dried over anhydrous Na₂SO₄, and concentrated in vacuo to yield a white solid (300 mg). LC-MS: 523 [M-tBu+H]⁺.

This solid (100 mg, 170 μmol) was dissolved in TFA (5 mL) and DCM (15 mL). The resulting mixture was stirred overnight. The mixture was evaporated in vacuo, and the residue was purified by preparative HPLC to yield the g title compound as a white solid (20 mg. LC-MS: 523.1 [M+H]+. ¹H-NMR: (DMSO-d₆): δ 2.14 (s, 3H), 3.17-3.16 (m, 2H), 4.11-4.08 (m, 2H), 4.26 (br, 1H), 4.98 (br, 2H), 5.50 (br, 1H), 7.58-7.36 (m, 7H), 9.94 (s, 1H), 13.8 (br, 1H).

F. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-ethoxyoxalylhydrazino]-2-hydroxypropionic Acid

Ethyl oxalyl chloride (12.4 μL, 111 μmol) was added to a solution of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid 2-oxo-2-phenylethyl ester (23.0 mg, 50 μmol) in DCM (413 μL, 6.4 mmol) at 0° C. and the resulting mixture was stirred at 0° C. for 15 minutes. Saturated aqueous NaHCO₃ (1 mL) was then added and the layers were separated. The aqueous layer was extracted with DCM (2×2 mL). The DCM layers were combined, dried over MgSO₄, and concentrated. Zinc (164 mg, 2.5 mmol) was added to a solution of this residue in AcOH (172 μL, 3.0 mmol) and the resulting mixture was stirred at room temperature for 10 minutes. The mixture was filtrated and the residue was purified by preparative HPLC to yield the title compound (10 mg). MS m/z [M+H]⁺ calc'd for C₂₀H₂₀ClFN₂O₆, 439.10. found 439.1.

G. (R)-3-[N-(5′-Chloro-2′-fluoro-iphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid 2,2-Difluoropropyl Ester

(R)-3-[N′-t-Butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]2-hydroxy-propionic acid (15.0 mg, 32 μmol) was combined with HOBt (26.0 mg, 193 μmol) and EDC (34 μL, 0.2 mmol) in DCM (0.2 mL, 4 mmol). The solution was stirred for 10 minutes and 2,2-difluoropropanol (24.7 mg, 257 μmol) was added. The reaction was stirred at room temperature and monitored for completion. After 2 hours, the mixture was concentrated by rotary evaporation and the solvent was removed in vacuo. The resulting residue was dissolved in DCM (124 μL, 1.9 mmol). TFA (124 μL, 1.6 mmol) was added, and the resulting mixture was stirred for 2 hours. The solvent was removed in vacuo and the residue was purified by preparative HPLC to yield the title compound (2.2 mg). MS m/z [M+H]⁺ calc'd for C₂₁H₂₀ClF₃N₂O₆, 489.10. found 489.1.

H. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid Isobutyl Ester

To a mixture of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid ethyl ester (HCl salt; 500.0 mg, 1.3 mmol) in DCM (6.0 mL, 94 mmol) at room temperature was added di-t-butyldicarbonate (342 μL, 1.5 mmol) and DIPEA (216 μL, 1.3 mmol). After stirring at room temperature overnight, the mixture was concentrated and the residue was purified by flash chromatography (12 g silica gel, 0-50% EtOAc/hexanes). The desired fractions were combined and concentrated to give a light yellowish oil. This oily residue was dissolved in MeOH (6.0 mL, 150 mmol) and water (1.0 mL, 56 mmol), then treated with LiOH monohydrate (104 mg, 2.5 mmol) at room temperature for 30 minutes. The mixture was concentrated and the residue was diluted with water (2.0 mL) and EtOAc (10.0 mL), then acidified with 1N aqueous HCl until pH˜2.0 with vigorous stirring. The organic layer was washed with saturated aqueous NaCl (2×2.0 mL), dried over Na₂SO₄, filtered, and concentrated to give Compound 1 as a white solid (528.6 mg).

Compound 1 (65.0 mg, 148 μmol) was dissolved in isobutyl alcohol (684 μL, 7.4 mmol). A solution of 4.0 M HCl in 1,4-dioxane (1.2 mL, 4.9 mmol) was added and the resulting mixture was stirred at room temperature for 2 hours, then at 60° C. for an other couple of hours, until the reaction was complete. The solvent was removed in vacuo to yield Compound 2, which was used without further purification.

t-Butyl oxalyl chloride was prepared by adding oxalyl chloride (63 μL, 741 μmol) to a solution of t-butyl alcohol (43 μL, 444 μmol) in ether (778 μL, 7.4 mmol). The mixture was stirred at room temperature for 15 minutes, then concentrated in vacuo. Compound 2 (58.5 mg, 148 μmol) was dissolved in DCM (570 μL, 8.9 mmol) and t-butyl oxalyl chloride was added. The resulting mixture was stirred at room temperature for 30 minutes and then concentrated in vacuo. The residue was dissolved in a 1:1 DCM:TFA solution and stirred at room temperature for 1 hour. The solvent was removed in vacuo and the residue was purified by preparative HPLC to yield the title compound (8.5 mg). MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClFN₂O₆, 467.13. found 467.0.

I. (R)-3-[N′-t-Butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic Acid Ethyl Ester

To a solution of (R)-3-[N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid ethyl ester (200 mg, 0.5 mmol) in DCM (2.0 mL) was added dropwise a solution of t-butyl oxalyl chloride (165 mg, 1.0 mmol) at 0° C. under nitrogen. The resulting mixture was stirred for 5 minutes and then DIPEA (130 mg, 1.0 mmol). was added dropwise. The solvent was removed by evaporation, and the residue was purified by column chromatography (petroleum ether/EtOAc=4:1) to yield the title compound as a yellow liquid (144 mg). LC-MS: 495 [M+H]⁺. ¹H NMR (CDCl₃, 400 MHz): δ 1.30 (t, J=7.1 Hz, 3H), 1.56 (s, 9H), 3.37-3.24 (m, 2H), 4.27-4.16 (m, 4H), 4.38-4.30 (m, 1H), 7.14-7.09 (m, 1H), 7.30-7.28 (m, 1H), 7.48-7.41 (m, 3H), 7.56-7.50 (m, 2H), 8.05 (s, 1H).

J. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxy-propionic Acid Ethoxycarbonyloxymethyl Ester

A mixture of (R)-3-[N′-t-butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid (270 mg, 580 μmol), chloromethyl ethyl carbonate (160 mg, 1.16 mmol), NaI (174 mg, 1.2 mmol) and 2,6-dimethylpyridine (620 mg, 5.8 mmol) in DMF (10 mL) was stirred at room temperature overnight. The mixture was poured into water (30 mL) and the mixture was then extracted with EtOAc (3×30 mL). The combined organic layers were washed with saturated aqueous NaCl (2×30 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo. The crude Compound 1 (300 mg) was used without purification. LC-MS: 569 [M+H]⁺.

TFA (1.0 mL) was added dropwise at room temperature to a solution of Compound 1 (300 mg, 530 μmol) in DCM (5 mL). The resulting mixture was stirred for 2 hours at room temperature, and the solvent was then removed. The residue was purified by column chromatography (DCM/MeOH, 10:1) to yield the title compound as a yellow liquid (10 mg). LC-MS: 512.9 [M+H]⁺. ¹H NMR (400 MHz, MeOD) δ 1.28 (t, J=7.3 Hz, 3H), 3.24-3.28 (m, 2H), 4.18-4.20 (m, 4H), 4.41 (br, 1H), 5.80 (dd, J=11.6, 5.8 Hz, 2H), 7.22 (d, J=10.1 Hz, 1H), 7.34-7.40 (m, 1H), 7.48-7.51 (m, 5H).

K. Butyric Acid (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionyloxymethyl Ester

A mixture of (R)-3-[N′-t-butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid (300 mg, 430 μmol), chloromethyl butyrate (175 mg, 1.3 mmol), NaI (192 mg, 1.3 mmol) and 2,6-dimethylpyridine (680 mg, 6.4 mmol) in DMF (10 mL) was stirred at room temperature overnight. The mixture was poured into water (30 mL) and the mixture was then extracted with EtOAc (3×20 mL). The organic layer was separated, washed with saturated aqueous NaCl (30 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo. The crude Compound 1 (300 mg) was used without purification. LC-MS: 567[M+H]⁺.

TFA (1.0 mL) was added dropwise at room temperature to a solution of Compound 1 (300 mg, 464 μmol) in DCM (5 mL). The resulting mixture was stirred for 2 hours at room temperature, and the solvent was then removed. The residue was purified by column chromatography (DCM/MeOH, 10:1) to yield the title compound as a yellow oil (21 mg). LC-MS: 511.1[M+H]⁺. ¹H NMR (400 MHz, MeOD) δ 0.94 (t, J=7.4 Hz, 3H), 1.62 (dd, J=14.8, 7.4 Hz, 2H), 2.33 (t, J=7.3 Hz, 2H), 3.28 (d, J=6.1 Hz, 2H), 4.14 (q, J=13.2 Hz, 2H), 4.38 (dd, J=6.0, 4.2 Hz, 1H), 5.80 (br, 2H), 7.16-7.26 (m, 1H), 7.33-7.40 (m, 1H), 7.47-7.52 (m, 5H).

L. (R)-3-[N-(5′-Chloro-2′-fluorobiphenyl-4-ylmethyl)-N′-oxalylhydrazino]-2-hydroxypropionic Acid Acetoxymethyl Ester

A mixture of (R)-3-[N′-t-butoxyoxalyl-N-(5′-chloro-2′-fluorobiphenyl-4-ylmethyl)hydrazino]-2-hydroxypropionic acid (300 mg, 640 μmol), bromomethyl acetate (196 mg, 1.3 mmol), NaI (192 mg, 1.3 mmol) and 2,6-dimethylpyridine (680 mg, 6.4 mmol) in DMF (10 mL) was stirred at room temperature overnight. The mixture was poured into water (30 mL) and the mixture was then extracted with EtOAc (3×20 mL). The organic layer was separated, washed with saturated aqueous NaCl (30 mL), dried over anhydrous Na₂SO₄, and concentrated in vacuo. The crude Compound 1 (300 mg) was used without purification. LC-MS: 539 [M+H]⁺.

TFA (1.0 mL) was added dropwise at room temperature to a solution of Compound 1 (300 mg, 550 μmol) in DCM (5 mL). The resulting mixture was stirred for 2 hours at room temperature, and the solvent was then removed. The residue was purified by column chromatography (DCM/MeOH, 10:1) to yield the title compound as a yellow oil (15 mg). LC-MS: 482.9 [M+H]⁺. ¹H NMR (400 MHz, MeOD) δ 2.07 (s, 3H), 3.25-3.28 (m, 2H), 4.14 (q, J=13.2 Hz, 2H), 4.38 (t, J=5.9 Hz, 1H), 5.88-5.71 (m, 2H), 7.25-7.17 (m, 1H), 7.41-7.31 (m, 1H), 7.70-7.46 (m, 5H).

Example 15 (2R,4S)-5-Biphenyl-4-yl-2-hydroxy-5-methyl-4-(oxalylamino)hexanoic Acid

(2R,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxy-5-methylhexanoic acid ethyl ester (70 mg, 0.2 mmol) was dissolved in DCM (5 mL) and stirred for 2 minutes, followed by the addition of ethyl oxalyl chloride (23 μL, 0.2 mmol) and DIPEA (79 mg, 0.6 mmol). The mixture was stirred at room temperature for 1 hour, then evaporated under reduced pressure. The mixture was the concentrated under vacuum. The residue was dissolved in EtOH, and sufficient equivalents of 10 N NaOH were added to make the solution basic. The reaction was monitored over 1 hour until final deprotection was complete. The solution was acidified with an equal volume of AcOH and evaporated under reduced pressure. The product was then purified using reverse phase chromatography (gradient of 10-70% MeCN to yield the title compound (37 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₁H₂₃NO₆, 386.15. found 386.4.

Example 16 (2S,4S)-5-Biphenyl-4-yl-2-hydroxymethyl-5-methyl-4-(oxalylamino)hexanoic Acid

(2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-5-methylhexanoic acid ethyl ester (HCl salt; 40 mg, 0.1 mmol) was dissolved in DCM and DMF (1 mL), followed by the addition of ethyl oxalyl chloride (17 μL, 0.2 mmol) and DIPEA (53.3 μL, 0.3 mmol). The mixture was stirred at room temperature until the reaction was complete (˜5 minutes). The reaction was quenched with water. The product extracted with EtOAc and the resulting organic layer was concentrated. 1 M aqueous lithium hydroxide (1.0 mL, 1.0 mmol) and EtOH (2.0 mL) was added and the mixture was stirred at room temperature until the reaction was complete (˜2 hours). The reaction was quenched with AcOH and the product was purified by preparative HPLC. The clean fractions were combined and lyophilized to yield the title compound (19 mg, purity 95%). MS m/z [M+H]⁺ calc'd for C₂₂H₂₅NO₆, 400.17. found 400.2.

Additional compounds of the invention can be prepared using the following starting materials:

(R)-4-Amino-5-biphen-4-yl-2-hydroxy-2-methyl-pentanoic Acid Ethyl Ester

To a solution of (R)-3-biphenyl-4-yl-2-t-butoxycarbonylamino-propionic acid (50 g, 0.1 mol), Meldrum's acid (23.3 g, 0.2 mol) and DMAP (27.8 g, 0.2 mol) in anhydrous DCM (500 mL) was added a solution of DCC (33.3 g, 0.2 mol) in anhydrous DCM (200 mL) over 1 hour at −5° C. under nitrogen. The mixture was stirred at −5° C. for 8 hours, then refrigerated overnight, during which tiny crystals of dicyclohexylurea precipitated. After filtration, the mixture was washed with 5% KHSO₄ (4×200 mL), saturated aqueous NaCl (200 mL) and dried under refrigeration with MgSO₄ overnight. The resulting solution was evaporated to yield crude Compound 1 as a light yellow solid (68 g). LC-MS: 490 [M+Na], 957 [2M+Na].

To a solution of crude Compound 1 (68 g, 0.1 mol) in anhydrous DCM (1 L) was added AcOH (96.8 g, 1.6 mol) at −5° C. under nitrogen. The mixture was stirred at −5° C. for 0.5 hour, then NaBH₄ (13.9 g, 0.4 mol) was added in small portions over 1 hour. After stirring at −5° C. for another 1 hour, saturated aqueous NaCl (300 mL) was added. The organic layer was washed with saturated aqueous NaCl (2×300 mL) and water (2×300 mL), dried over MgSO₄, filtered, and concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=5:1) to yield Compound 2 as a light yellow solid (46 g). LC-MS: 476 [M+Na], 929 [2M+Na].

To a solution of Compound 2 (46 g, 0.1 mol) in tertiary butyl alcohol (100 mL) was added dimethylmethyleneimmonium iodide (46.3 g, 0.3 mol) at room temperature under nitrogen. The mixture was heated to 65° C. and stirred at this temperature for 16 hours. After filtration, the filtrate was concentrated to give the crude product which was further purified by chromatography (hexanes:EtOAc=20:1˜10:1) to yield Compound 3 as a light yellow solid) (18 g). LC-MS: 460 [M+Na], 897 [2M+Na].

To a solution of Compound 3 (18 g, 44 mmol) in acetone (430 mL) and water (22 mL) was added Sudan Red as indicator. Ozone atmosphere was introduced into the mixture at 0° C. until the red color of Sudan Red disappeared. Dimethyl sulfide (45 mL) was added and the mixture was stirred at room temperature overnight. The mixture was then concentrated and the residual was purified by chromatography (hexanes:EtOAc=15:1˜7:1) to yield Compound 4 as a light yellow solid (9.5 g). LC-MS: 434 [M+H], 845 [2M+H].

To a solution of Compound 4 (9.5 g, 23 mmol) in anhydrous THF (120 mL) was added a solution of methylmagnesium bromide in THF (9.2 mL, 28 mmol) at −70° C. under nitrogen. The mixture was stirred at −60° C. for 3 hours and the reaction was then quenched with saturated aqueous NH₄Cl (50 mL). The organic layer was separated and dried over MgSO₄. The mixture was then concentrated and the residual was purified by chromatography (hexanes:EtOAc=10:1˜5:1) to yield Compound 5 as an oil (7.9 g). LC-MS: 450 [M+H], 877 [2M+H].

To a solution of Compound 5 (7.9 g, 18.4 mmol) in anhydrous DCM (300 mL) was pumped HCl atmosphere at 0° C. for 6 hours. The mixture was then concentrated and the residue was washed with anhydrous Et₂O to yield the title compound as a white solid HCl salt (5.8 g). LC-MS: 364 [M+H], 727 [2M+H]. ¹H NMR (300 MHz, DMSO): δ8.00-7.97 (d, 4H), 7.67-7.62 (m, 6H), 7.47-7.28 (m, 8H), 6.32 (s, 1H), 6.09 (s, 1H), 4.13-4.06 (m, 2H), 3.95-3.78 (m, 2H), 3.60 (s, 1H), 3.22-3.08 (m, 3H), 2.95-2.65 (m, 2H), 1.99-1.79 (m, 4H), 1.30-0.87 (m, 9H).

(R)-4-Amino-5-biphenyl-4-yl-2,2-dimethyl-pentanoic Acid Ethyl Ester

A solution of [(S)-1-biphenyl-4-ylmethyl-2-(2,2-dimethyl-4,6-dioxo-[1,3]dioxan-5-yl)-ethyl]-carbamic acid t-butyl ester (46 g, 0.1 mol) in anhydrous toluene (300 mL) was refluxed for 3 hours under nitrogen. After evaporation of the solvent, the residue was purified by chromatography (hexanes:EtOAc=10:1) to yield Compound 1 as a light yellow solid (27 g). LC-MS: 374 [M+Na], 725 [2M+Na].

To a solution of Compound 1 (6.2 g, 17.6 mmol) in anhydrous THF (100 mL) was added a solution of LiHMDS in THF (39 mL, 39 mmol) at −78° C. under nitrogen. The mixture was stirred at −78° C. for 2 hours, and then methyl iodide (7.5 g, 53 mmol) was added. After stirring for 0.5 hour at −78° C., the mixture was warmed to room temperature and stirred at room temperature for 3 hours. After the mixture cooled to −10° C., the reaction was quenched with saturated aqueous NH₄Cl (100 mL) and extracted with EtOAc (100 mL×4). The combined organic layers were washed with saturated aqueous NaCl (300 mL), dried over MgSO₄, filtered, and concentrated to yield the crude product which was further purified by chromatography (hexanes:EtOAc=10:1) to yield Compound 2 as a light yellow solid (5.7 g). LC-MS: 402 [M+Na], 781 [2M+Na].

To a solution of Compound 2 (5.7 g, 15 mmol) in acetone (120 mL) was added 1 M NaOH (60 mL, 60 mmol) at −5° C. under nitrogen. The mixture was warmed to room temperature and stirred at room temperature for 20 hours. The mixture was concentrated and the residual was diluted with water (250 mL) and washed with EtOAc (150 mL). The pH of the aqueous layer was adjusted to 2 with 6 M HCl at 0° C., and the solid was filtrated and dried in vacuo to yield the crude Compound 3 as a white solid (5 g). LC-MS: 420 [M+Na], 817 [2M+Na].

To a solution of crude Compound 3 (5 g, 12.7 mmol) in anhydrous EtOH (300 mL) was added SOCl₂ (13.4 mL, 190 mmol) at −30° C. under nitrogen. The mixture was warmed to room temperature and stirred for 20 hours at room temperature. The mixture was concentrated, and the residual was washed with anhydrous Et₂O to yield the title compound as a white solid HCl salt (3.7 g). LC-MS: 326 [M+H], 651 [2M+H]. ¹H NMR (300 MHz, DMSO): δ7.86 (s, 3H), 7.67-7.64 (m, 4H), 7.49-7.33 (m, 5H), 4.09-3.97 (m, 2H), 3.42 (m, 1H), 2.90-2.80 (m, 2H), 1.88-1.84 (m, 2H), 1.17-1.12 (m, 9H).

1-((R)-2-Amino-3-biphenyl-4-yl-propyl)-cyclopropanecarboxylic Acid

Into a flask containing BOC-D-4,4′-biphenylalanine (11.3 g, 33.1 mmol, 1.0 eq.), 4-dimethylaminopyridine (6.5 g, 53.0 mmol, 1.6 eq.), 2,2-dimethyl-1,3-dioxane-4,6-dione (5.3 g, 36.4 mmol, 1.1 eq.) in DCM (100 mL) was added 1 M of DCC in DCM (38.1 mL) at 0° C. over 30 minutes. The mixture was maintained at 0° C. for 6 hours and the resulting precipitate was filtered off. The filtrate was washed with aqueous 10% KHSO₄ (2×50 mL) then dried. The solution was acidified with AcOH (20 mL) at 0 OC and sodium borohydride (3.1 g, 82.7 mmol, 2.5 eq.) was added over 30 minutes in 3 portions. The mixture was maintained at 0° C. for 3 hours, washed with water and dried, then concentrated under vacuum. The crude material was purified by chromatography (0-40% EtOAc/hexanes gradient). Eschenmoser's salt (15.9 g, 86.0 mmol) in t-butyl alcohol (70 mL) was added and the resulting mixture was stirred at 65° C. overnight. The mixture was concentrated and Et₂O (10 mL) was added. The organic solution was then washed with saturated aqueous NaHCO₃ (10 mL) and 10% KHSO₄ (10 mL). The organic solution was dried over Na₂SO₄ and concentrated. The crude product was purified by chromatography (0-40% EtOAc/hexanes gradient) to yield Compound 1 (3.3 g).

Trimethylsufoxonium iodide (2.0 g, 9.2 mmol, 1.0 eq.) in dimethyl sulfoxide (50 mL) was combined with NaH (366 mg, 9.2 mmol, 1.1 eq.) amd stirred for 15 minutes at room temperature. To this was added Compound 1 (3.6 g, 8.3 mmol, 1.0 eq) dissolved dimethyl sulfoxide (50 mL). The resulting mixture was stirred at room temperature overnight. The solution was mixed with saturated aqueous NaCl (50 mL) and extracted with EtOAc (3×10 mL), and the organic layer was washed with saturated aqueous NaCl (2×50 mL) and dried over anhydrous Na₂SO₄. After evaporation of the solvent, the crude reaction was purified by chromatography (0-40% EtOAc/hexanes gradient) to yield Compound 2, 1-((R)-3-biphenyl-4-yl-2-t-butoxycarbonylaminopropyl)-cyclopropanecarboxylic acid t-butyl ester. TFA (200 μL) and DCM (500 μL) were added and the resulting mixture was stirred for 30 minutes. The solvent was evaporated under vacuum and azeotroped with toluene (2×) to obtain the title compound.

Assay 1 In Vitro Assays for the Quantitation of Inhibitor Potencies at Human and Rat NEP, and Human ACE

The inhibitory activities of compounds at human and rat neprilysin (EC 3.4.24.11; NEP) and human angiotensin converting enzyme (ACE) were determined using in vitro assays as described below.

Extraction of NEP Activity from Rat Kidneys

Rat NEP was prepared from the kidneys of adult Sprague Dawley rats. Whole kidneys were washed in cold phosphate buffered saline (PBS) and brought up in ice-cold lysis buffer (1% Triton X-114, 150 mM NaCl, 50 mM tris(hydroxymethyl)aminomethane (Tris) pH 7.5; Bordier (1981) J. Biol. Chem. 256: 1604-1607) in a ratio of 5 mL of buffer for every gram of kidney. Samples were homogenized on ice using a polytron hand held tissue grinder. Homogenates were centrifuged at 1000×g in a swinging bucket rotor for 5 minutes at 3° C. The pellet was resuspended in 20 mL of ice cold lysis buffer and incubated on ice for 30 minutes. Samples (15-20 mL) were then layered onto 25 mL of ice-cold cushion buffer (6% w/v sucrose, 50 mM pH 7.5 Tris, 150 mM NaCl, 0.06%, Triton X-114), heated to 37° C. for 3-5 minutes and centrifuged at 1000×g in a swinging bucket rotor at room temperature for 3 minutes. The two upper layers were aspirated off, leaving a viscous oily precipitate containing the enriched membrane fraction. Glycerol was added to a concentration of 50% and samples were stored at −20° C. Protein concentrations were quantitated using a BCA detection system with bovine serum albumin (BSA) as a standard.

Enzyme Inhibition Assays

Recombinant human NEP and recombinant human ACE were obtained commercially (R&D Systems, Minneapolis, Minn., catalog numbers 1182-ZN and 929-ZN, respectively). The fluorogenic peptide substrate Mca-D-Arg-Arg-Leu-Dap-(Dnp)-OH (Medeiros et al. (1997) Braz. J. Med. Biol. Res. 30:1157-62; Anaspec, San Jose, Calif.) and Abz-Phe-Arg-Lys(Dnp)-Pro-OH (Araujo et al. (2000) Biochemistry 39:8519-8525; Bachem, Torrance, Calif.) were used in the NEP and ACE assays respectively.

The assays were performed in 384-well white opaque plates at 37° C. using the fluorogenic peptide substrates at a concentration of 10 μM in Assay Buffer (NEP: 50 mM HEPES, pH 7.5, 100 mM NaCl, 0.01% polyethylene glycol sorbitan monolaurate (Tween-20), 10 μM ZnSO₄; ACE: 50 mM HEPES, pH 7.5, 100 mM NaCl, 0.01% Tween-20, 1 μM ZnSO₄). The respective enzymes were used at concentrations that resulted in quantitative proteolysis of 1 μM of substrate after 20 minutes at 37° C.

Test compounds were assayed over the range of concentrations from 10 μM to 20 pM. Test compounds were added to the enzymes and incubated for 30 minute at 37° C. prior to initiating the reaction by the addition of substrate. Reactions were terminated after 20 minutes of incubation at 37° C. by the addition of glacial acetic acid to a final concentration of 3.6% (v/v).

Plates were read on a fluorometer with excitation and emission wavelengths set to 320 nm and 405 nm, respectively. Inhibition constants were obtained by nonlinear regression of the data using the equation (GraphPad Software, Inc., San Diego, Calif.):

ν=ν₀/[1+(I/K′)]

where ν is the reaction rate, ν₀ is the uninhibited reaction rate, I is the inhibitor concentration and K′ is the apparent inhibition constant.

Compounds of the invention were tested in this assay and found to have pK_(i) values at human NEP as follows. In general, either the prodrug compounds did not inhibit the enzyme in this in vitro assay, or the prodrugs were not tested (n.d.) since activity would not be expected.

Ex. pK_(i) 1 7.0-7.9 2A ≧9 2B n.d. 2C n.d. 2D n.d. 2E n.d. 2F ≧9 2G 8.0-8.9 2H ≧9 2I 8.0-8.9 2J 7.0-7.9 2K n.d. 2L n.d. 2M n.d. 2N ≧9 2O n.d. 2P n.d. 2Q n.d. 2R n.d. 2S n.d. 2T ≧9 2U ≧9 2V ≧9 2W 3A ≧9 3B n.d. 3C n.d. 3D ≧9 4 8.0-8.9 5-1 ≧9 5-2 n.d. 5-3 n.d. 5-4 n.d. 5-5 ≧9 5-6 n.d. 5-7 n.d. 5-8 n.d. 5-9 ≧9 5-10 n.d. 5-11 n.d. 5-12 n.d. 5-13 ≧9 5-14 ≧9 5-15 ≧9 5-16 n.d. 5-17 ≧9 6A ≧9 6B n.d. 7A n.d. 7B ≧9 8-1 n.d. 8-2 ≧9 8-3 ≧9 8-4 8.0-8.9 8-5 8.0-8.9 8-6 7.0-7.9 9A 8.0-8.9 9B n.d. 10 8.0-8.9 11-1 8.0-8.9 11-2 ≧9 11-3 7.0-7.9 11-4 8.0-8.9 12 7.0-7.9 13 8.0-8.9 14A ≧9 14B n.d. 14C 8.0-8.9 14D n.d. 14E n.d. 14F 8.0-8.9 14G n.d. 14H n.d. 14I n.d. 14J n.d. 14K n.d. 14L n.d. 15 7.0-7.9 16 8.0-8.9 n.d. = not determined

Assay 2 Pharmacodynamic (PD) Assay for ACE and NEP Activity in Anesthetized Rats

Male, Sprague Dawley, normotensive rats are anesthetized with 120 mg/kg (i.p.) of inactin. Once anesthetized, the jugular vein, carotid artery (PE 50 tubing) and bladder (flared PE 50 tubing) catheters are cannulated and a tracheotomy is performed (Teflon Needle, size 14 gauge) to faciliate spontaneous respiration. The animals are then allowed a 60 minute stabilization period and kept continuously infused with 5 mL/kg/h of saline (0.9%) throughout, to keep them hydrated and ensure urine production. Body temperature is maintained throughout the experiment by use of a heating pad. At the end of the 60 minute stabilization period, the animals are dosed intravenously (i.v.) with two doses of AngI (1.0 g/kg, for ACE inhibitor activity) at 15 minutes apart. At 15 minutes post-second dose of AngI, the animals are treated with vehicle or test compound. Five minutes later, the animals are additionally treated with a bolus i.v. injection of atrial natriuretic peptide (ANP; 30 g/kg). Urine collection (into pre-weighted eppendorf tubes) is started immediately after the ANP treatment and continued for 60 minutes. At 30 and 60 minutes into urine collection, the animals are re-challenged with AngI. Blood pressure measurements are done using the Notocord system (Kalamazoo, Mich.). Urine samples are frozen at −20° C. until used for the cGMP assay. Urine cGMP concentrations are determined by Enzyme Immuno Assay using a commercial kit (Assay Designs, Ann Arbor, Mich., Cat. No. 901-013). Urine volume is determined gravimetrically. Urinary cGMP output is calculated as the product of urine output and urine cGMP concentration. ACE inhibition is assessed by quantifying the % inhibition of pressor response to AngI. NEP inhibition is assessed by quantifying the potentiation of ANP-induced elevation in urinary cGMP output.

Assay 3 In Vivo Evaluation of Antihypertensive Effects in the Conscious SHR Model of Hypertension

Spontaneously hypertensive rats (SHR, 14-20 weeks of age) are allowed a minimum of 48 hours acclimation upon arrival at the testing site with free access to food and water. For blood pressure recording, these animals are surgically implanted with small rodent radiotransmitters (telemetry unit; DSI Models TA11PA-C40 or C50-PXT, Data Science Inc., USA). The tip of the catheter connected to the transmitter is inserted into the descending aorta above the iliac bifurcation and secured in place with tissue adhesive. The transmitter is kept intraperitoneally and secured to the abdominal wall while closing of the abdominal incision with a non-absorbable suture. The outer skin is closed with suture and staples. The animals are allowed to recover with appropriate post operative care. On the day of the experiment, the animals in their cages are placed on top of the telemetry receiver units to acclimate to the testing environment and baseline recording. After at least of 2 hours baseline measurement is taken, the animals are then dosed with vehicle or test compound and followed out to 24 hours post-dose blood pressure measurement. Data is recorded continuously for the duration of the study using Notocord software (Kalamazoo, Mich.) and stored as electronic digital signals. Parameters measured are blood pressure (systolic, diastolic and mean arterial pressure) and heart rate.

Assay 4 In Vivo Evaluation of Antihypertensive Effects in the Conscious DOCA-Salt Rat Model of Hypertension

CD rats (male, adult, 200-300 grams, Charles River Laboratory, USA) are allowed a minimum of 48 hours acclimation upon arrival at the testing site before they are placed on a high salt diet. One week after the start of the high salt diet (8% in food or 1% NaCl in drinking water), a deoxycorticosterone acetate (DOCA) pellet (100 mg, 90 days release time, Innovative Research of America, Sarasota, Fla.) is implanted subcutaneously and unilateral nephrectomy is performed. At this time, the animals are also surgically implanted with small rodent radiotransmitters for blood pressure measurement (see Assay 3 for details). The animals are allowed to recover with appropriate post operative care. Study design, data recording, and parameters measured is similar to that described for Assay 3.

Assay 5 In Vivo Evaluation of Antihypertensive Effects in the Conscious Dahl/SS Rat Model of Hypertension

Male, Dahl salt sensitive rats (Dahl/SS, 6-7 weeks of age from Charles River Laboratory, USA) are allowed at least 48 hours of acclimation upon arrival at the testing site before they were placed on a 8% NaCl high salt diet (TD.92012, Harlan, USA) then surgically implanted with small rodent radiotransmitters for blood pressure measurement (see Assay 3 for details). The animals are allowed to recover with appropriate post operative care. At approximately 4 to 5 weeks from the start of high salt diet, these animals are expected to become hypertensive. Once the hypertension level is confirmed, these animals are used for the study while continued with the high salt diet to maintain their hypertension level. Study design, data recording, and parameters measured is similar to that described in Assay 3.

Comparative Example 1

(2R,4S)-5-Biphenyl-4-yl-2-methyl-4-(oxalyl-amino)-pentanoic Acid (Comparative Compound A; R═—C(O)—COOH)

(2R,4S)-4-Amino-5-biphenyl-4-yl-2-methyl-pentanoic acid ethyl ester (HCl salt; 527 mg, 0.2 mmol) and ethyl oxalyl chloride (18.4 μL, 1.1 eq) were combined with DIPEA (52.2 μL, 0.3 mmol) in DMF (0.3 mL)/DCM (0.3 mL). The mixture was stirred at room temperature until the reaction was complete. The solvent was removed and the residue was dissolved in EtOH (750 μL) and 1 M aqueous NaOH (750 μL), and stirred at room temperature overnight. The solvent was removed and the residue was purified by preparative HPLC to yield Comparative Compound A (11.2 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₀H₂₁NO₅, 356.14. found 356.2.

(2R,4S)-5-Biphenyl-4-yl-4-(3-carboxy-propionylamino)-2-methyl-pentanoic Acid (Comparative Compound B; R═—C(O)—(CH₂)₂—COOH)

(2R,4S)-5-Biphenyl-4-yl-4-(3-carboxy-propionylamino)-2-methyl-pentanoic acid ethyl ester (Na salt; 400 mg, 923 μmol) was mixed with EtOH (7 mL, 0.1 mol) then THF (6 mL, 0.1 mol). 1 M Aqueous NaOH (2.8 mL, 2.8 mmol) was then added and the resulting mixture was stirred at room temperature for 4 hours and was then concentrated. The product was purified by preparative HPLC (10-60% MeCN:water w/0.5% TFA) to yield Comparative Compound B (150 mg, 97% purity). MS m/z [M+H]⁺ calc'd for C₂₂H₂₅NO₅, 384.17. found 384.6.

Comparative Compounds A and B were tested as described in Assay 1 and found to have pK_(i) values at human NEP as follows:

Compound R pK_(i) Comparative Compound A —C(O)—COOH 8.2 Comparative Compound B —C(O)—(CH₂)₂—COOH 8.2 The data shows that Comparative Compounds A and B have the same pK_(i) values for the inhibition of NEP.

Comparative Example 2

(R)-5-Biphenyl-4-yl-4-(2-carboxyacetylamino)-2-hydroxypentanoic Acid (Comparative Compound C; R═—C(O)—CH₂—COOH)

(R)-4-Amino-5-biphenyl-4-yl-2-hydroxypentanoic acid ethyl ester (HCl salt; 60.3 mg, 0.2 mmol) and methyl malonyl chloride (21 μL, 0.2 mmol) were combined with DIPEA (84 μL, 0.5 mmol) in DMF (5 mL). The mixture was stirred at room temperature until the reaction was complete (1 hour). The solvent was removed and the residue was dissolved in MeOH (3 mL) and 10 N NaOH (250 μL), and stirred at 60° C. until the reaction was complete (1 hour). Glacial acetic acid (250 μL) was added and the product was evaporated under reduced pressure and purified by preparative HPLC to yield Comparative Compound C (6.3 mg, 98% purity). MS m/z [M+H]⁺ calc'd for C₂₀H₂₁NO₆, 372.14. found 372.2.

(R)-5-Biphenyl-4-yl-4-(3-carboxypropionylamino)-2-hydroxypentanoic Acid (Comparative Compound D; R═—C(O)—(CH₂)₂—COOH)

(R)-4-Amino-5-biphenyl-4-yl-2-hydroxypentanoic acid ethyl ester (HCl salt; 60.3 mg, 0.2 mmol) and 3-(carbomethoxy)propionyl chloride (24 μL, 0.2 mmol) were combined with DIPEA (84 μL, 0.5 mmol) in DMF (5 mL). The mixture was stirred at room temperature until the reaction was complete (1 hour). The solvent was removed and the residue was dissolved in MeOH (3 mL) and 10 N NaOH (250 μL), and stirred at 60° C. until the reaction was complete (1 hour). Glacial acetic acid (250 μL) was added and the product was evaporated under reduced pressure and purified by preparative HPLC to yield Comparative Compound D (8.0 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₁H₂₃NO₆, 386.15. found 386.2.

(R)-5-Biphenyl-4-yl-4-(4-carboxybutyrylamino)-2-hydroxypentanoic Acid (Comparative Compound E; R═—C(O)—(CH₂)₃—COOH)

(R)-4-Amino-5-biphenyl-4-yl-2-hydroxypentanoic acid ethyl ester (HCl salt; 60.3 mg, 0.2 mmol) and methyl 5-chloro-5-oxovalerate (31.7 mg, 0.2 mmol) were combined with DIPEA (84 μL, 0.5 mmol) in DMF (5 mL). The mixture was stirred at room temperature until the reaction was complete (1 hour). The solvent was removed and the residue was dissolved in MeOH (3 mL) and 10 N NaOH (250 μL), and stirred at 60° C. until the reaction was complete (1 hour). Glacial acetic acid (250 μL) was added and the product was evaporated under reduced pressure and purified by preparative HPLC to yield Comparative Compound E (8.7 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₂H₂₅NO₆, 400.17. found 400.2.

The compound of Example 1 and Comparative Compounds C, D, and E were tested as described in Assay 1 and found to have pK_(i) values at human NEP as follows:

Compound R pK_(i) Example 1 —C(O)—COOH 7.9 Comparative Compound C —C(O)—CH₂—COOH 6.7 Comparative Compound D —C(O)—(CH₂)₂—COOH 7.4 Comparative Compound E —C(O)—(CH₂)₃—COOH 7.3 The data shows that the compound of Example 1 had higher potency at NEP than Comparative Compounds C, D, and E.

Comparative Example 3

(2S,4S)-5-Biphenyl-4-yl-4-(2-carboxy-acetylamino)-2-hydroxymethylpentanoic Acid (Comparative Compound F: R═—C(O)—CH₂—COOH)

(2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid (HCl salt; (5 mg, 10 μmol) was dissolved in 1 μM aqueous NaOH (119 μL, 119 μmol) and slowly added to a solution of methyl malonyl chloride (1.9 μL, 18 μmol) and MeCN (0.5 mL, 10 mmol). The resulting solution was stirred at room temperature until the reaction was complete (overnight) and the product was purified by preparative HPLC to yield Comparative Compound F (1.0 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₁H₂₃NO₆, 386.15. found 386.1.

(2S,4S)-5-Biphenyl-4-yl-4-(3-carboxy-propionylamino)-2-hydroxymethylpentanoic Acid (Comparative Compound G; R═—C(O)—(CH₂)₂—COOH)

(2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid (HCl salt; (5 mg, 10 μmol) was dissolved in 1 M aqueous NaOH (119 μL, 119 μmol) and slowly added to a solution of 3-(carbomethoxy)propionyl chloride (2.2 μL, 18 μmol) and MeCN (0.5 mL, 10 mmol). The resulting solution was stirred at room temperature until the reaction was complete (overnight) and the product was purified by preparative HPLC to yield Comparative Compound G (3.4 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₂H₂₅NO₆, 400.17. found 400.3.

(2S,4S)-5-Biphenyl-4-yl-4-(4-carboxy-butyrylamino)-2-hydroxymethylpentanoic Acid (Comparative Compound H; R═—C(O)—(CH₂)₃—COOH)

(2S,4S)-4-Amino-5-biphenyl-4-yl-2-hydroxymethyl-pentanoic acid (HCl salt; (5 mg, 10 μmol) was dissolved in 1 M aqueous NaOH (119 μL, 119 μmol) and slowly added to a solution of methyl 5-chloro-5-oxovalerate (2.5 μL, 18 μmol) and MeCN (0.5 mL, 10 mmol). The resulting solution was stirred at room temperature until the reaction was complete (overnight) and the product was purified by preparative HPLC to yield Comparative Compound H (3.0 mg, 95% purity). MS m/z [M+H]⁺ calc'd for C₂₃H₂₇NO₆, 414.18. found 414.7.

The compound of Example 5A and Comparative Compounds F, G, and H were tested as described in Assay 1 and found to have pK_(i) values at human NEP as follows:

Compound R pK_(i) Example 5A —C(O)—COOH 9.2 Comparative Compound F —C(O)—CH₂—COOH 8.2 Comparative Compound G —C(O)—(CH₂)₂—COOH 9 Comparative Compound H —C(O)—(CH₂)₃—COOH 8.6 The data shows that the compound of Example 5A had higher potency at NEP than Comparative Compounds F, G, and H.

Comparative Example 4

(2R,4R)-4-(2-Carboxy-acetylamino)-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic Acid (Comparative Compound I; R═—C(O)—CH₂—COOH)

Methyl malonyl chloride (18.5 μL, 172 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (50.0 mg, 144 μmol) and DIPEA (75.1 μL, 431 μmol) in DCM (1.5 mL, 23.4 mmol) and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was then concentrated to yield a yellow liquid. 1 M Aqueous LiOH (719 μL, 719 μmol) was added dropwise to the oil, and the mixture was stirred at 60° C. for 1 hour. The mixture was concentrated in vacuo and the resulting residue was dissolved in AcOH (1.0 mL) purified by preparative HPLC to yield Comparative Compound I (2.0 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₀H₂₀ClNO₆, 406.10. found 406.1.

(2R,4R)-4-(3-Carboxy-propionylamino)-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic Acid (Comparative Compound J; R═—C(O)—(CH₂)₂—COOH)

3-(Carbomethoxy)propionyl chloride (21.2 μL, 172 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (50.0 mg, 144 μmol) and DIPEA (75.1 μL, 431 μmol) in DCM (1.5 mL, 23.4 mmol) and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was then concentrated to yield a yellow liquid. 1 M Aqueous LiOH (719 μL, 719 μmol) was added dropwise to the oil, and the mixture was stirred at 60° C. for 1 hour. The mixture was concentrated in vacuo and the resulting residue was dissolved in AcOH (1.0 mL) purified by preparative HPLC to yield Comparative Compound J (31.1 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₁H₂₂ClNO₆, 420.11. found 420.2.

(2R,4R)-4-(4-Carboxy-butyrylamino)-5-(3′-chloro-biphenyl-4-yl)-2-hydroxy-pentanoic Acid (Comparative Compound K; R═—C(O)—(CH₂)₃—COOH)

Methyl 5-chloro-5-oxovalerate (23.8 μL, 172 μmol) was added to a solution of (2R,4R)-4-amino-5-(3′-chlorobiphenyl-4-yl)-2-hydroxypentanoic acid ethyl ester (50.0 mg, 144 μmol) and DIPEA (75.1 μL, 431 μmol) in DCM (1.5 mL, 23.4 mmol) and the resulting mixture was stirred at room temperature for 30 minutes. The mixture was then concentrated to yield a yellow liquid. 1 M Aqueous LiOH (719 μL, 719 μmol) was added dropwise to the oil, and the mixture was stirred at 60° C. for 1 hour. The mixture was concentrated in vacuo and the resulting residue was dissolved in AcOH (1.0 mL) purified by preparative HPLC to yield Comparative Compound K (29.2 mg, 100% purity). MS m/z [M+H]⁺ calc'd for C₂₂H₂₄ClNO₆, 434.13. found 434.2.

The compound of Example 2A and Comparative Compounds I, J, and K were tested as described in Assay 1 and found to have pK_(i) values at human NEP as follows:

Compound R pK_(i) Example 2A —C(O)—COOH 9.7 Comparative Compound I —C(O)—CH₂—COOH 8.4 Comparative Compound J —C(O)—(CH₂)₂—COOH 9.5 Comparative Compound K —C(O)—(CH₂)₃—COOH 9.3 The data shows that the compound of Example 2A had higher potency at NEP than Comparative Compounds I, J, and K.

While the present invention has been described with reference to specific aspects or embodiments thereof, it will be understood by those of ordinary skilled in the art that various changes can be made or equivalents can be substituted without departing from the true spirit and scope of the invention. Additionally, to the extent permitted by applicable patent statutes and regulations, all publications, patents and patent applications cited herein are hereby incorporated by reference in their entirety to the same extent as if each document had been individually incorporated by reference herein. 

1. A compound of formula I:

where: R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R¹⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR¹¹R¹², —CH(R¹⁵)—NH₂, —CH(R¹⁵)—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R¹¹ and R¹² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R¹¹ and R¹² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R¹³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR¹¹R¹²; and R¹⁴ is —C₁₋₆alkyl or —C₀₋₆alkylene-C₆₋₁₀aryl; R¹⁵ is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl; R² is —CH₂OR²¹; and R³ is —CH₃; where R²¹ is H, —C(O)—C₁₋₆alkyl, —C(O)—CH(R²²)—NH₂, —C(O)—CH(R²²)—NHC(O)O—C₁₋₆alkyl, or —P(O)(OR²³)₂; R²² is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl; R²³ is H, —C₁₋₆alkyl, or phenyl; or Z is selected from —CH— and —N—; R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,

R⁴⁰ is selected from —C₁₋₆alkyl, —O—C₁₋₆alkyl, —C₃₋₇cycloalkyl, —O—C₃₋₇cycloalkyl, phenyl, —O-phenyl, —NR⁴¹R⁴², —CH(R⁴⁵)—NH₂, —CH(R⁴⁵)—NHC(O)O—C₁₋₆alkyl, and —CH(NH₂)CH₂COOCH₃; and R⁴¹ and R⁴² are independently selected from H, —C₁₋₆alkyl, and benzyl; or R⁴¹ and R⁴² are taken together as —(CH₂)₃₋₆—, —C(O)—(CH₂)₃—, or —(CH₂)₂O(CH₂)₂—; R⁴³ is selected from —O—C₁₋₆alkyl, —O-benzyl, and —NR⁴¹R⁴²; and R⁴⁴ is —C₁₋₆alkyl or —C₀₋₆alkyl or —C₆₋₁₀aryl; R⁴⁵ is H, —CH₃, —CH(CH₃)₂, phenyl, or benzyl; a is 0 or 1; R⁵ is selected from halo, —CH₃, —CF₃, and —CN; b is 0 or an integer from 1 to 3; each R⁶ is independently selected from halo, —OH, —CH₃, —OCH₃, —CN, and —CF₃; where each alkyl group in R¹ and R⁴ is optionally substituted with 1 to 8 fluoro atoms; and where the methylene linker on the biphenyl is optionally substituted with one or two —C₁₋₆alkyl groups or cyclopropyl; or a pharmaceutically acceptable salt thereof.
 2. The compound of claim 1, where R¹ is H.
 3. The compound of claim 1, where R¹ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R¹⁰, —C₁₋₆alkylene-NR¹¹R¹², —C₁₋₆alkylene-C(O)R¹³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,


4. The compound of claim 1, where R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₆alkylene-OC(O)R¹⁰, and

where R¹⁰ is —C₁₋₆alkyl, —O—C₁₋₆alkyl, or —CH[R¹⁵]—NHC(O)O—C₁₋₆alkyl; R¹⁴ is —C₁₋₆alkyl; R¹⁵ is —CH(CH₃)₂; and each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms.
 5. The compound of claim 4, where R¹ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —(CH₂)₆CH₃, —CH₂CF₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —CH₂CF₂CF₃, —CH₂OC(O)CH₃, —CH₂OC(O)CH₂CH₃, —CH₂OC(O)(CH₂)₂CH₃, —CH₂OC(O)OCH₂CH₃, —CH₂OC(O)—CH[CH(CH₃)₂]—NHC(O)O—CH₃, and

where R¹⁴ is —CH₃. 6-8. (canceled)
 9. The compound of claim 1, where R² is —CH₂OR²¹, R³ is —CH₃, and R²¹ is H.
 10. The compound of claim 1, where R⁴ is H.
 11. The compound of claim 1, where R⁴ is selected from —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-C₆₋₁₀aryl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —C₁₋₃alkylene-C₁₋₉heteroaryl, —C₃₋₇cycloalkyl, —[(CH₂)₂O]₁₋₃CH₃, —C₁₋₆alkylene-OC(O)R⁴⁰, —C₁₋₆alkylene-NR⁴¹R⁴², —C₁₋₆alkylene-C(O)R⁴³, —C₀₋₆alkylenemorpholinyl, —C₁₋₆alkylene-SO₂—C₁₋₆alkyl,


12. The compound of claim 1, where R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, and

where R⁴⁴ is —C₁₋₆alkyl; and each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms.
 13. The compound of claim 12, where R⁴ is selected from H, —CH₂CH₃, —CH(CH₃)₂, —CH₂CH(CH₃)₂, —(CH₂)₃CH₃, —C(CH₃)₃, —(CH₂)₂CF₃, —CH₂CF₂CH₃, —(CH₂)₃—O—CH₂CH₃, —(CH₂)₂—O-phenyl, —(CH₂)₂OCH₃, and

where R⁴⁴ is —CH₃.
 14. The compound of claim 1, where a is 0, or a is 1 and R⁵ is halo.
 15. The compound of claim 1, where b is 0, or b is 1 and R⁶ is halo, or b is 2 and each R⁶ is independently selected from halo and —CH₃.
 16. The compound of claim 1, where: a is 0 and b is 0; or a is 0, b is 1, and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro; or a is 0, b is 2, and R⁶ is 2′-fluoro, 5′-chloro or 2′-methyl, 5′-chloro or 2′,5′-dichloro; or a is 1, R⁵ is 3-chloro, and b is 0; or a is 1, R⁵ is 3-chloro, b is 1, and R⁶ is 3′-chloro; or a is 1, R⁵ is 3-chloro, b is 2, and R⁶ is 2′-fluoro, 5′-chloro. 17-22. (canceled)
 23. The compound of claim 9, where R¹ is H or —C₁₋₈alkyl; Z is —CH—; R⁴ is H or —C₁₋₈alkyl; a is 0; and b is 0, or b is 1 and R⁶ is halo.
 24. The compound of claim 23, where R¹ is H or —CH₂CH₃; R⁴ is H or —CH₂CH(CH₃)₂; and b is 0, or b is 1 and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro.
 25. The compound of claim 1, where R¹ is selected from H, —C₁₋₈alkyl, —C₁₋₆alkylene-OC(O)R¹⁰, and

where R¹⁰ is —C₁₋₆alkyl, —O—C₁₋₆alkyl, or —CH[R¹⁵]—NHC(O)O—C₁₋₆alkyl; R¹⁴ is —C₁₋₆alkyl; R¹⁵ is —CH(CH₃)₂; and each alkyl group in R¹ is optionally substituted with 1 to 8 fluoro atoms; R⁴ is selected from H, —C₁₋₈alkyl, —C₁₋₃alkylene-O—C₁₋₈alkyl, —C₁₋₃alkylene-O—C₆₋₁₀aryl, —[(CH₂)₂O]₁₋₃CH₃, and

where R⁴⁴ is —C₁₋₆alkyl; and each alkyl group in R⁴ is optionally substituted with 1 to 8 fluoro atoms; a is 0 and b is 0; or a is 0, b is 1, and R⁶ is 2′-fluoro, 3′-fluoro, 3′-chloro, or 4′-flouro; or a is 0, b is 2, and R⁶ is 2′-fluoro, 5′-chloro or 2′-methyl, 5′-chloro or 2′,5′-dichloro; or a is 1, R⁵ is 3-chloro, and b is 0; or a is 1, R⁵ is 3-chloro, b is 1, and R⁶ is 3′-chloro; or a is 1, R⁵ is 3-chloro, b is 2, and R⁶ is 2′-fluoro, 5′-chloro; and where the methylene linker on the biphenyl is optionally substituted with two —CH₃ groups.
 26. The compound of claim 25, where R² is —OR²¹ or —CH₂OR²¹; and R³ is H or —CH₃; where R²¹ is H. 27-28. (canceled)
 29. A pharmaceutical composition comprising the compound of claim 1 and a pharmaceutically acceptable carrier. 30-32. (canceled)
 33. (2S,4R)-5-(5′-chloro-2′-fluorobiphenyl-4-yl)-2-hydroxymethyl-2-methyl-4-(oxalyl-amino)pentanoic acid or a pharmaceutically acceptable salt thereof. 